Hi, I Have 2 Questions. One, I Have Been Having

Hi, I have 2 questions. One, I have been having bad pain on my right lower back. Sometimes it is hard to walk it hurts so bad especially in the morning. Not sure what it could be. Also I have gained a significant amount of weight in my mid section and was wondering if it could be a health problem. I went to the obgyn and im good with those parts and my thyroid is good as well. I just dont want to ignore it if it can be a major health issue. Just curious