Do you have a thick discharge as well? If so, it sounds like Thrush.... very very common in pregnancy. I got it when I was 30 weeks and it drove me insane!!!!!! it wasn't itchy at first, just red, swollen and sore. I went to the pharmacy and they gave me Canestan 3 day treatment. It's a cream which instantly relieves the itchyness and soreness and also comes with an applicator to put the cream "up there" but they told me to only insert it halfway. Worked a treat.

If you're not sure, you may be best asking your GP, but i'd say that's what it is.

Hope it clears up for you soon, it's no fun at all!