Can't stop throwing up

Ok so I have been throwing up for the last month almost every night. It hits me after I eat dinner and I seem the throw up everything that I ate that day. I am not loosing weight I can keep liquids down. The doctor has done a lot of tests to find the cause and the only test that has came back wrong is that I have a low potassium level at 3.2 normal being 3.5-5.0 she has done a head CT which came back normal and several other tests all normal but I am still throwing up and have no energy. Does anyone have any suggestions.......I feel like I'm loosing it I can't keep living like this