If you haven't done this yet, you should start keeping a journal to record what you eat, how you feel before/after meals, what your bowel movements are like (how frequent, appearance). This will help you and your doctor understand better what's going on with your stomach ache.
My symptoms really became noticable during my first pregnancy - I became lactose intolerant, which is not so unusual, but caused me a lot of gas, nausea and pain until I started adding lactase pills to my meals. Maybe that's something for you to consider for yourself - most adults are lactose intolerant to some degree. What I discovered later is that my lactose intolerance is better wor worse depending on the status of my Crohn's disease - inflammation in the ileum affects lactase production which therefore makes me feel worse if I eat a lot of dairy during a flare.
There seems to be some new evidence also about gluten intolerance - I don't know if your doctor has mentioned this to you, but it may be something to consider also. Many adults are being diagnosed with this condition later in life - it has generally been thought that you either can or cannot digest gluten, and that you'd discover this in childhood, but this theory seems to be failing.
My diagnosis with Crohn's took many years. I think that's a very common experience. The path to a diagnosis for me started with bloody stools and diarrhea, and got more focused with the addition of joint pain and fatigue. I feel a lot better with the right medications, which also helps confirm the diagnosis.
I hope that you get some relief from your pain and a more helpful diagnosis soon.