Period Problems. Help! Please...!!!?!?!?!?

OK! SO, I got my period last wednesday, and I really needed to go to the nurse to get my pad. And of course I was freaking out beacause i've never had my period before and its really overwhelming when it comes on the worst possible day. Any way. The tacher let me go, bad thing, i'm in 7th grade, the guys are really immature, and there were 2 in there. Luckily they both left before she isted me, but what do I do if she asks me first. Do I whisper? OH! And My period is really heavy, will it be heavy just the first time, or every time? And I'm really athletic, so what if I have a game, and I need to change really bad, but i'm not allowed to leave. I have to run 3 miles every time I leave the gym, all my coaches are guys! How do I take a shower if im gonna get blood all over the towel in athletics? UGH! LIFE IS HARD!