Why Am I Having Back Pain After Putting A Tampon In?

Ok so I'm 14 and I've had my period since I was about 12 so 2 years my period is very heavy and risently I have had alot of lower back pain to the point of missing school and soccer and everything but if I take the tampon out it stops herting but then I can't play soccer or do any thing with out a tampon so what's wrong am I puting the tampon in wrong