Do not feel guilty and assume other women are handling their lives better. They may be at times, but we all have massive slumps. Your list of things troubling you are very difficult things, especially all piled up. It's great you can identify them and voice your frustration.
If I were you, I would pick a few things that I COULD improve, and take a little action on just those. Making a little headway will make you feel better in general, and able to handle a few other things.
I'm recently coming out of a pregnancy at 40, husband always gone, massive IRS issues, no budget for help of any kind with 3 kids under 5, no money for nice things-at times I start to flip out. But you know what, ALWAYS, it is ALWAYS about counting your blessings to feel better, and reaching out to other people, I know it sounds cliche, but it's always true.
Sure, we're on a shoestring budget and constant stress, but for now I have a roof over my head, electricity, and time home with healthy kids without working full time like I did my whole life before taking this "break". I truly believe anyone with a healthy child, or two or three and no serious medical issues has no right to complain (for me, not saying you're complaining), because anything could happen any minute, and you haven't appreciated what you had...etc...you know all that.
What really got me down on a superficial level with the finances and the pregnancies, was that my appearance really went to hell. I had a high risk pregnancy with lots of bed reast and gained TONS of weight, meanwhile, no budget at all for any decent maternity outfits or hair upkeep etc. My skin was horrible etc. Then once my 3rd baby was here, I had no help and no budget still, so I was still in the crappy cheap maternity clothes forever.
ANYWAY. That's what I zoned in on first. My husband was away a lot, so I made a pledge to get on track, lose the weight, pick up a couple of very cheap new things here and there as the weight came off, found a way to renew my gym membership (with daycare) at a discount by begging the owner for help, ate restorative good simple healthy food and got my skin on track, wore make-up, got my hair to cooperate a bit, and TRIED to be nice and cheerful to my husband again, not sad because I felt ugly. Each day was a little bit better than the last, and I felt SO much better once I got on track with that.
Next I made a pact not to let the IRS looming catastrophic project get me down. I just refused. I did the tasks I had to, but I also counterbalanced it with something nice and fun for the kids each day. We just spent time, not money. I accepted that bankruptcy or losing the house might lie ahead, but I wasn't going to feel bad before I knew. It's still looming. I still don't care! My husband helps with nothing-he's not home! I spend way too much time dealing with it, and it's not fair, its my husband's debt form a corrupt scenario by his accountants at the time, but I made the mistake of filing jointly for the years in question. So what, nothing new, One day at a time. Counting blessings.
One of my favorite books is A New Earth, and I always remember not to overwhelm myself with cumulative problems including past and future, but to really take one day at a time, one hour at a time, and I always, pray prayers of thanks and ask for a little strength to turn my attitude around every day. Sometimes several times. A nice list of all my blessings, out loud, and giving sincere thanks.
It's understandable to miss your mother. Allow yourself that, but realize when you are letting it make you depress yourself. She wants you to be happy.
Your bonus(?) is that a step daughter? THAT is a tough one. You just need to love yourself, and NOT let her get to you. I know it seems impossible and easy for me to say. I don't know her age, but if she is out of toddler years, there is no harm saying, "It's OK if you don't like me. I understand. I don't like everyone either." Try to just sort of steer clear of her except to be nice, like you are, do nice things for her, uphold your rules and then buzz off when she turns sour. Remind yourself you know why she is doing this. Do not take it to heart. It won't last forever. She will not always be young enough to be manipulated by her mom. Just be a good person. Isolate it in your mind, address it mentally, and move on with the day as many times as it takes, do not let it gang up on you. Remember your blessings.
Potty training-SUCKS!!! It takes FOREVER. I've given up 4 times too-my son's still not trained. It will get solved.
I counted myself lucky that my husband isn't harsh, and did not make my life hard or bring me down during that slump, even though I was not that fabulous chick he married. I've bounced back.
I have to do all the work around here, I'm the only one stressed while my husband is off on tour not dealing with daily finances, but its worth many other things. Nothing has to be permanent. One day at a time.
You may be done having kids, You may not. Don't pre-worry. Work on yourself and your health, and enjoy your un-potty trained precious little son.
If I were you, I would address your physical appearance and health a little first, to perk yourself up. I would also ACT happy even before you feel it, at least a few times a day. Do something nice each day for your husband or one of the kids, just for self therapy. Next I would do something above and beyond at your job-since you're feeling inadequate there. Do something extra in some way. Just one day. Then something the next. A few days later, reach out to one old friend. They will be happy to hear from you. Ask about THEM and do not dwell on yourself. I find that focusing on others ALWAYS makes me feel better. Don't sweat the family-I'm glad none of mine are close. You only need a couple of good friends. Reach out and make them. Force yourself.
Don't say your husband is a good man BUT he could help out more. Say he's a good man and treat him like gold. He'll help out more, when you're being happier and doing extra things for him-it always works that way. Ask him if you can splurge and get a cleaning service to give the house a fresh start.
You are a beautiful and important woman, and you can believe it if you take action. Treat those around you with the love you wish you had for yourself at work and at home, and things will get better. Give yourself daily things to do, but don't overwhelm yourself,and take one day at a time. Be good to yourself. Treat your appearance and health like they are important-they are. Your family loves you and your step daughter will too one day. This will pass. Blessings-these times are really hard, you'll make it!