What Causes Swelling And Pain In The Testicles?

I had a bike accident when I was a young, and a few years later I had an operation to lower my testicular as they had not dropped back down from the accident. They are only just below by penis, and the right one will sometimes go back in and if I am having sex it can get squashed and be very painful, I am also to shy to undress in front of others if I am having a shower after golf, or going swimming and will not use a public toilet, only a cubicle. I have no problems ejaculating. Is there some way I can lower them, make them look bigger, I have put up with this for to long and more than happy if it mean plastic surgery but all I can find is for twisted or cryptorchidism that is not me as they are down just not so anyone can see most of the time.