Chest and upper back pains after exercising?

Yesterday was the first day of volleyball tryouts..I haven't exercised all winter which wasn't smart and now I'm paying for it. It was a 7hr day, involving core exercises(sit-ups, pushups, jumping, etc) and a LOT of running. Well, besides being somewhat tired after wasn't too bad until that night around 11pm. (we finished at 6) since 11 last night and still this afternoon I've had chest pains that include my upper back that have kept me from sleeping much. It feels tight..sort of a stabbing pain at the same time. I sort of have a hard time breathing too and it's a little scary but I ume its because of the sudden strenuous activity. Help? Anyone have any idea if that's why or if I pulled something, etc? I'm sorta worried and need to get back to practice by tomorrow if i wanna make the team :( thanks in advance