Yeast infection or PID?

Before anyone can ask no it's not an STD because I never had actual sex. I went to the beach 3 weeks ago and last week my period started off heavy and hurt like hell. So currently it's been a few days after my period ended and my vagina itched a lot and a sharp pain I sense in side and my vaginal region is so itchy, dry, and it's irratated and burns my firends suggest I got an infection from the dirty beach water that I was recently told had really bad bacteria in florida, used my new feminine wash too much that it throw off my PH, or I sat in my period blood and got an infection from. Any thoughts?