I was around 200 when I got pregnant with my third child. Because I was already overweight, my doctor recommended that I only gain between 15-20 pounds. That allows for plenty of nutrients for the growing baby (and you), amniotic fluid, the baby, the placenta, breast tissue growth and only about 5 pounds of maternal fat stores (for breastfeeding). I ended up gaining around 23 pounds because I had severe swelling towards the end, but I'm so glad I didn't gain 30-40 pounds like I did with my other two children.
I didn't obsess about my weight. I just tried to be as healthy as I could be. I ate healthy foods in moderation, took a daily walk, got plenty of rest (which helps with cravings. Tired people sometimes eat more to make up for lack of energy), drank plenty of water and took my vitamin.
You shouldn't try to lose weight while pregnant. No doctor would recommend that. A small amount of weight loss during the 1st trimester because of morning sickness is normal and a couple of pounds lost around your due date is normal too. But I've never heard of a doctor advocating weight loss during pregnancy.
My son is now 7 months old and I'm currently 18 pounds lighter than I was when I got pregnant with him, so having another baby won't stop you from reaching your goal if you're committed. Good luck to you!