PLEASE HELP

okay so i'm having this problem with my vagina and i looked up so many things. the opening to my vagina hole is kinda swollen, it happened after me and my boyfriend had sex for the 4th time, and it was quick and not really rough, and i'm not allergic to latex and i'm almost positive it isn't a std or and sti. i dont know if it's a yeast infection or something else like bacterial vaginosis? but i know this is tmi, but after i orgasm the swelling stops and it goes back to normal. i started taking monistat and it went down a lot but i have to stop because i wear tampons and they said don't use it with tampons, but i started it back up and it's helping a little but not a lot. someone please help me i'm just confused and a little scared....