Odd swelling

Tia

So since last week I’ve been having swelling down there. I’ve taken Advil and I brought the swelling down a little bit but it would come right back. I went to the Obgyn today and they said they can see it’s swollen but they aren’t sure why. They told me to take a bath and see if that helps big that doesn’t even help. My step mother said it’s because I’m getting my period but I never had this happen before I get my period. Anyone know why or have any ideas? I have to wear right undies or it will hurt to walk😐 I’m in loss of words. HELP