tmi, but help.

I'm 31 weeks pregnant,  and lately I was having this real bad itch In my vagina. Really bad. And was so painful. But there was no smell. It seems to be everytime me and my boyfriend have sex. Now it's got progressively worse, I'm not getting this yellow coloured discharge that has a really weird and very strong odour, as well as still being itchy. And this is like, 2 days after sex I'll get this. What could it be????