Painful Hip And Abdominal Area, Normal Cholesterol, Blood Pressure. Done Ultrasound Of Kidney. Help?

Hi, I am a healthy 45 year old female and I can't understand why my eGFR ranges from 50-59. I have always exercised alot, my blood pressure and cholesterol are great and my weight is good. Both of my parents are deceased, and I don't think there is a family history, but I'm not sure. I was given an ultrasound of the kidneys and bladder but it came back normal. . At times I do drink excess alchol and I wonder if that is the reason. When I was younger I would offen drink excessively. I also get sharp pains, mostly on my right side, just in line with the top of my hip and in a little. Once it was so intense I couldn't move for about 45 mins, but mostly its a niggering pain daily. My doctor does'nt seen concerned and said I dont need to go and see a specialist at this point. I don't want to wait until my kidneys decrease further until I find out the problem why this is happening. Do you think I should recieve other tests and do you think alchol could of caused this?