Post hip replacement problems

I had hip replacement 6 days ago and the first two days went according to everything I was told but on the third day I tried to walk around and I had excruciating pain in my lower leg down the tibia or shin bone and my knee and the side of my knee was horrible burning pressure tingling just a deep deep ache. I kept trying to walk but it would make me cry out. Went back to orthopedics they did an x-ray and there was no fracture. But they really don't know what's wrong he put me on gabapentin for possible nerve damage somewhere and this is my first day taking it I'm not feeling great on it in fact I feel like I couldn't even get up and try to walk for feeling a little unstable. I just wondered if anyone else had that problem and did it resolve on its own or did they find the right solution? I go back next week for my first visit and I'm praying for some progress as I take these pills and get through the next days of hopefully being a little active.