Struggling

I am very overweight, 20 weeks pregnant, and struggling. I had lost 130lbs over a two year timeframe and then fell off track majorly and gained 100lbs back over about a year and then got pregnant. This is our first child and is very wanted and we are so excited but I really didn't want to be this size while pregnant. I wanted to be healthy and exercising and eating right. I want to look pregnant, not just fat. Now I am having terrible back pain and generally feel like crap and I can't imagine how I am going to get through the next 20 weeks let alone go through labor. I want to try to get better but I really don't know where to start. Getting through the day is just so much effort and painful. I am so overwhelmed. Does anyone have any suggestions? Any other mommas to be in my boat?