Anyone experts on knees? MRI and Xray negative but chronic pain?

Late May I bent sideways on one leg, my knee shifted inward and it made a loud pop. I couldn't bend it so it was either locked or something, kind of forgot. Anyways, I went to the doctor a week later (orthopedic) and wanted an X-ray, he said it's just a sprained MCL especially since my symptoms point tot hat. A lot of people asked me why I had an X-ray rather than an MRI because x-rays aren't helpful for things other than bones which makes sense. Anyway, I was given a hinged knee brace when I saw the doc the first time. Used crutches for five weeks and even though the doc said I could stop using my brace, I always use it when I go out somewhere because it feels a lot more stable that way. I went to physical therapy for a few weeks until now (only 8 more visits till the insurance no longer covers it) and the p.t. said she thinks it's a torn meniscus instead of a sprain since it clicks a lot and catches sometimes. So the doctor had me do an MRI last week, that was also negative and he told me to keep icing it and go to physical therapy. I will be getting a second opinion from another doc on monday but I'm curious to see if anyone here knows things about this or if it has happened to them. Every day I'm in pain, i stopped taking motrin because it stopped working. i can't walk for very long, when I do it clicks. i definitely can't even jog without it hurting (the other day i ran across the street and it hurt the rest of the day), can't bend it for very long, when i do a deep leg bend it hurts. on those incline boards (did it at the p.t.) if i lean forward with my legs straight it doesn't pop but when I bend my legs and lean forward then straighten them back up my knee definitely pops and its very painful. I've also done thigh curls with only a 10lb and it still hurts and clicks.