My right knee feels like i have a rubberband in front of the knee it's stiff cracks, clunks it's also a bit painful behind the knee slightly right?

Could be a meniscus: A torn meniscus or a loose body could give you these symptoms. Any injuries in the past? Does it lock? Does it have full range of motion?

Knee: See your GP and get a examination of the Joint. Sometimes meniscal pathology, arthritis can cause this. You are young so don't expect arthritis . Likely to be lax ligaments or meniscus.