What could it be? TMI!!!

So I been having unprotected sex with my bf for about 6-7 months which is about the same amount of time I been on depo. And my period has been nonstop since August. But lately I notice that I been have a lil itch and burning when I wipe or wash up. And today when I looked its just look like a red patch on both sides of my outer lower lips. I think its just rashes from constantly wearing pads but I still wanna make sure it's not an sti. Idk if you can really see the red patches but do anyone kno any products I could use to get rid of them?