I have pain below my right knee cap been going on 2 months-about once a week. no relation to activity or inactivity?

Cartilage or tendon : Most likely there is some degeneration of the cartilage under your knee cap. This is called chondromalacia patella. The other likely possibility if it is only below the knee cap would be patella tendinitis . Less likely would be a problem in the knee joint such as an inflamed fat pad behind the tendon or an anterior meniscus problem.