Why is my heel and tendon always sore?

I'm in middle school,8th grade and usually around lunch while i'm playing football my heel and tendon start to hurt and get worse with time.Every day they are fine but get sore around lunch again.Sometimes its so bad I can't walk.What do you think is up with that?I have always been athletic and I'm one of the best players so it sucks being sucky and I have pumas if that helps...please help and should I see a doctor?