Need Advice

Hey guys! Here is a bit of info on me
I have had two beautiful sons, my oldest turns three in August and my youngest is turning 8 months on the 29th. I just had to have an abortion for medical reasons, I was 8 weeks along and had gained roughly 8-9 pounds. Both of my sons were given up for adoption, both for different reasons (and at different times), and I have a goal to work on myself, along with a lot of other things in life.
My entire life has been spent in an abusive home, where I was never pushed to do anything. I didn't have to go to school if I didn't want to, I could eat whatever I wanted, I got away with everything. Would you believe I was adopted by these people?
I have severe bi polar disorder. I also have a milk allergy that was abused by my parents. I was given goats milk when I was 9 days old, instead of the soy formula I needed. I have a problem eating dairy, I hate the smell and taste of milk & yogurt.
Oh and I am sensitive to corn bread/corn meal. My entire life was spent eating junk food. Ramen, pizza rolls, Dr. Pepper, corn dogs(They did make me sick, but I had no idea I was allergic), donuts, cookies, CRAP. I only liked broccoli with a ton of velveeta cheese & carrots and ranch. I ate it rarely but still liked it a bit. No fruits.

When I hit puberty at about 13, I was around the size of a junior 3 in pants and a small in t-shirts. By the time I met my (now) husband at age 16, I was in a size 11 in juniors and worse large t-shirts. After my first son, and then the adoption, I went from about 160 pounds to 190 pounds from depression. I was in a size 14. After my second son, I was in a size 16. After this third pregnancy, and almost hitting 200 pounds (I can't imagine how big I'd be if I would of gone through with the pregnancy) I am now in a size 18. I am 5'7" by the way.

I will be starting culinary school next month, and I am trying to figure out how I will be able to get through the pastry portion without turning into a hog. I can't try new foods, but boy I sure will want to try when I start baking at school!!
I have no idea HOW to learn to be a chef, if I don't try things, and trying things can cause to weight gain. I also can't try new foods because of the digestive problem.

I'm scared, no, terrified that I will be this fat - stretch marked - cellulite - acned lady my whole life! I don't want my husband to have to wake up to this every morning, I want to be sexy for him. :sigh: