I am having knee problems help please?!

I am having knee problems help please?

About a year ago I crashed on my bike going down a hill...I smashed my knee's into the ground...and my head...and of course my hands...ofter I got up I realised I had rocks embedded in my hands and very big bruises on my knees...and of course my head was bleeding...After a few weeks I was up and running again... I went to the doctor about 4 months ago and they just said I had pulled a tendon...but....the pain in my knees isn't constant. It will hurt for about a month..then stop for a few weeks.... I tried taking almost every pain killer on the shelf..and none of them work even a little bit...

and do you think my stunt biking is stopping them from healing right...i mean its exercise so shouldn't it help?

Anyone have any idea's of what is going on?
I could really use the help....

2 weeks ago
I am 14...I don't think a 50 tear old would be stunt biking xD

And Helmet...last helmet I had cost 90 dollars...And I broke it :\
don't have money to get another at the moment

Stunt biking may be exercise, but probably not the kind your knee needs for rehabilitation. Talk to your doctor about your pain and the need for physical therapy. They will teach you the right kind of exercise to promote strength, healing, and pain relief.