I've experienced that pain...it reminded me of when I was a young teenager and my legs would ache badly and Mum would tell me it was "growing pains" - muscles and tendens stretching because I was growing. Well, obviously I still wasn't growing in my mid to late 40s when the pain came back (sometimes my legs would go numb as I was walking down the stairs and I felt like I could fall any minute). I remember nights lying in bed and just not being able to get comfortable because I had unexplained leg ache.
I never did go to the doctor and it did eventually go away. I don't know if it was directly related to my weight but have to admit I haven't experienced it in a couple of years. I'm glad you went to the doctor and he ran all the tests - if nothing showed up then perhaps it IS weight related (either that or you're starting to age, my dear)