Swollen feet at 37 weeks pregnant?

I was told I had gestational diabeties at 28 weeks pregnant, I have to check my levels 7 times a day. Last week I was told that the tummy on the baby was still huge (even tho all I ate was salads and great fruit and veg) and I would have to inject insulin twice a day, since then my feet have swollen twice the size and i was wondring I'd it was to do with the insulin. Please help