See a general doc first, and let him refer you to the right one. See, it's hard to pinpoint which specialist, on account of you have several diff symptoms that point to completely different things. The back pain, that could be a trapped nerve or ruptured disc, and as a result you cannot walk well. BUT you also hae abdominal pain, which doesn't usually happen with a bad back, so could be it's all a digestive issue where you are constipated or something like that. AND THEN you have this inner thigh problem, which can be from your lymph glands that are located there might be trying to rid your body of some infection, so could be those things are in trouble and causing your other symptoms. So, you see why I say you should see a GP first, and let him narrow it down to who you should go to. But mainly I DO think it's a neurological problem, in which case if you feel you must go directly to a specialist, a neurologist is the doc to see.
Dear Kelljeanhen, welcome to the medhelp forum. You need to be seen by a general physician first. These symptoms could be interrelated due to a pinched nerve or disc degeneration causing low back and inner thigh pain causing difficulty in walking. Lower abdominal pain could be due to several causes like GERDS, intestinal colic, renal or ureteric stones, abdominal mass, obstruction, irritable bowel syndrome. Let a GP evaluate you first and depending on his findings, you can be referred to the appropriate specialist. You can furnish more detailed history for us to help you further and specifically. Wish you all the best. Take care.