Help with identifying stomache problem?

A couple of weeks before i had a pain in my stomach that i would get after eating in the morning, i cut out acidic foods and even took anti acids which made my stomach feel sick and the pain still persisted. There was no heartburn, although my stomach was upset and a sick nausea feeling would last for 1-2 hours. It eventually went away after a week of battling it, cutting out different foods that i thought was affecting it. Now my problem is i eat at 6-7pm for the last couple nights, and have woken up to stomach pain and nausea which i have to sit up, more so stand up to get it to go away. It has affected my sleep and caused me a great deal of suffering, could anyone help me? I don't think its an ulcer, because i can eat in the morning and I'm fine its just during the night time. I also wait 3-4 hours before going to bed, and i hardly drink water to neutralize the acids, so what could be the problem? it would be GREATLY APPRECIATED if a fellow human could pinpoint key factors or maybe the problem... thank you for taking time to read and help me identify the problem !!!!!!