Working out and eating healthy to stay fit

I'm currently 7 weeks pregnant but I already have my pregnancy and post pregnancy body on the brain. I look everyday in the mirror and love my body and I don't want to be one of those moms that end up with a sloppy body or pouch after pregnancy. I've always been naturally fit and had the indention for a 6 pack but I never worked it all the way through. Now I'm scared pregnancy is going to wreck my body. 

 I initially wanted to go one a vegan/ vegetarian diet through my pregnancy. My plan was to stop eating red meat and pork the first 3 months, then stop chicken next 3 months, then stop eating seafood the last 3 months and stick to just raw fruits and veggies throughout the delivery my child's first 6 months. I've been getting mixed reactions to that since people feel my unborn baby needs the meat. And it has been kind of hard to stick with my plan.

Also I want to work out but since I'm in my first trimester I don't want to do anything too stressful.I'm not big on running but I love to dance and I enjoy stretching. I want to get into Pilates but the pregnancy based classes they offer in my area are only for ladies who are later in their pregnancy.

Any suggestions or help I would really appreciate. 

Thank you!