I say this having divorced my daughter's father when she was 4, being a single mom for 8 years and I got re-married last December.
If there is ANY POSSIBLE WAY to save your marriage.... not just live in a mediocre marriage, but save your marriage that should be where ALL YOUR ENERGY GOES. period.
Your happiness counts, but I would say it doens't count as much as the happiness of your kids. That's what being a parent is... you have vowed to provide a stable, loving, home for your kids. If you don't honor that vow and you don't honor the vow you made to your husband you are setting up a role model for you kids that "your word" means nothing and they won't respect you. how could they?
How do you know this new man is a good fit for you? Because the chemistry is there? what will happen to that chemistry when you are juggling visitation and child support issues and all of the things that come with sharing custody? That can wreck a relationship faster than you can say "the grass is not greener".
So, no. I wouldn't get divorced if I was in an "ok" marriage. I would make that marriage better. And I would raise my child(ren) will full access to BOTH parents.
If you want to divorce when they are out of your house.... maybe then you can be selfish. You can't be selfish when your kids are young. Because then you teach your kids to be selfish. So, if you want to throw you kids into chaos.... then yes, divorce their dad and immediately bring a new man into the picture. Good luck with that. In my opinion you are going to have sooooo many more problems with your kids after you do that. You think it's going to be good because you have chemistry with this man? How long have you known him? Do you have similar child raising philosophies? How will you handle when you son gets angry? I don't mean angry over a toy.... I mean MONTHS of anger over your divorce? I mean angry when he hates this new man who you are replacing his dad with? I mean ANGRY for months. How will that affect your chemistry?
I don't mean to sound harsh. I didn't have the option to stay with my daughter's dad. He filed for divorce and left. I would have stayed and tried to work it out then.... and based on how it has affected my daughter I would tell you it would have been MUCH better for her to have us still married, so that she could have stable relationship with BOTH her parents. We didn't have that choice But I took my time to work through my issues and her issues before dating and before getting re-married. We have a good thing now, but it takes WORK no matter what relationship you are in.
You should look at YOURSELF. have you been the best wife to HIM that you could be? Have you taken care of yourself? Have you sought counseling... both individual and together so that you can work on these issues? What does your husband want in a marriage? Is he a good father? These are all things you should explore before making the decision to leave. And when you leave the LAST person you should get involved with is "Mr we have chemistry".
Just my $0.02. Good luck with whatever path you choose. You will ALL need it.