Really need advice!

Anna

Im 17 and lost my virginity at 15 (my sophmore year) I was a little sore afterwords but i had to run the mile at school that day for PE and ever since then when I work out a lot or run I get these really really painful cramps like a super bad period but im too scared to go to the doctors and tell mymom. Has this happened to anyone else/does anyone have some advice?