Gaining weight

I have had an awful time with my weight this pregnancy. I gained 10 lbs before I found out I was pregnant. Then I gave into my cravings and slept alot through the first trimester, gained more weight. Then I hurt my back at work in the beginning of my second trimester. I could only do stretching until I was about 26 weeks. Gained more weight being immobile. Now I'm in my third trimester I am so out of shape when I try to do any exercise I lose my breath and get sick and dizzy since I am out of shape and huge. Somedays I eat to be healthy, somedays I forget to eat, and other days I eat too much. I figure, I am already this big and I can't diet and exercise until I give birth. I am worried about how hard labor will be since I am out of shape this time. Now I am 36 weeks and have gained almost 50lbs! :-/ I can wait to have my baby in my arms, and my body back! I plan on breast feeding but at least I won't feel bad about over exertion while exercising will deprive the baby of oxygen or I will pass out. Some days I have to make myself eat but I don't want to keep getting bigger and bigger. I hope my baby comes soon, I am struggling to stay sane and love myself at this point. Please Come out, anytime now little one!