To everyone who gets stomach aches from a change in meds, or meds of any kind (except NSAIDS which cause gastric problems) CHECK THE INGREDIENTS!!!! It doesn't have to do where it comes from! It might have to do with putting lactose or gluten in the meds as an inactive ingredient! You might have become gluten or lactose intolderant! The USA has gone to large contracts and the drugs are cheaply made. The VA was feeding me medications for two years (NOT looking at my medication profile!) and I was getting stomach aches from the meds. The pharmacist finally called me to say they can't supply my meds because of the contracts. One day we should get together and make the manufacturers CHANGE the formulations. Because they CAN. The solution is taking a lactaid/lactase pill with the medication. If it helps then that is the problem. You've got to complain. Also I want to caution you about the "numbness" in your feet. If you stop the gabapentin and it resolves you know it was causal. IF it doesn't, than it means the numbness is an impinged nerve root exiting your lumbar spine and not the medicine. Good luck. I hated the gabapentin even at the smallest dose. Do exercises stretching your lumbar out. I finally had lumbar fusion in 2019. It fixed the numbness but need more 6 years later as I only had a small piece done and more is deteriorating. Had a great epidural yesterday in the facet joint area, fixed me right up. Hope it will last for a bit! I have degenerative disc disease so its a process.