You have really sufferred with this! I think you should talk to your doctor about this pain. It could be arthritis even though it only hurts at night. As a fellow side sleeper, I recommend trying a pillow between your knees at night. Not only does this help my knees but it also helps my back. If it does help, do not let it keep you from seeing a doctor. Arthritis is a degenerative condition that needs to be treated for your quality of life. Keep hiking! You are blessed and an inspiration.
I had the exact same thing for quite some time. What I found out that it really wasn't my KNEE...it was actually inflammation in my back pinching a nerve which I FELT in my knee. I got so irritated during the MRI because the doc and technician kept talking about my back but it was my knee that hurt. Anyhooo, putting a pillow (a nice firm thick one) and putting your right leg on it and I'll bet you'll have some relief. Surprisingly when you lay on your side (either side), that position of one leg on top of the other actually works the lower back muscle! I really hope this helps. I'm a side sleeper and I'm not a happy camper when I have to sleep on my back.
Oh, and when I finally went to the doc..I found out I did have arthritis. I always take a hot shower before bed and that helps.