Derrick... If you feel quite comfortable from a playing standpoint with the guitar fairly high, but putting your left leg that high gives you back pain, then the solution may well be a guitar support. There are a number of fairly popular ones around--Gitano, Ergoplay, Dynarette, etc--but the place to start is to scroll through the forum. There are a number of threads discussing the pros and cons of each right here on the ergonomics board.
Good luck with it. Back pain sucks.
“People may say I can’t sing, but no one can ever say I didn’t sing.” --Florence Foster Jenkins