Tummy tighten exercises

Anyone know any exercises to tighten and tone your belly while pregnant? The top of my belly is rounded and hardened by the bottom is flat and hangs like a pancake, it's disgusting and I'm self conscious about it. I'm obese on a chart. I'm 22 weeks 6 days I'm 5'5" and weigh 201 pounds? I've only gained 7 pounds so far since my pregnancy. I just want to look more pregnant so I can embrace it a little more people keep trying to touch my stomach and I feel like I come off rude because I freak out. I'm worried they're gonna feel how fat and gross I am (I try to hide it with clothes and wear leggings over the gross part. Any ideas? I'm really embarrassed about my body I gained 40 pounds at my desk job then I got pregnant and I'm afraid to work out and hurt my baby. OB said I can't lift or do anything vigorous. I can swim, walk and go on the elliptical is what he said, but I want something else to focus on tightening my stomach!