I have a female question about menstruation...?

Is it normal for a woman to swell a little and get sore in the vaginal area during menstruation? It only does it when I'm menstruating. I got kind of worried but I can't get anything done at the doctor until after... but it doesn't do it after.

I have recently switched to tampons instead of pads. I change both every 3-4 hours and I alternate between the two. I am on birth control and have been since I was 15 (I'm 19 now.) I'm not sexually active. I use the birth control to regulate my periods because I was having multiple ones a month. The yearly gynecologist appointment said everything was fine when I went a few months ago so it's not cancer or anything like that.

Any ideas / comments that you may think would help are highly appreciated.