i am experiencing this more often in past years especially since 60, requiring anti nausea med. never comes on in daytime. have never liked milk but now cut it out in the main, only drink water. also cut out wheat in the main. i also,have ibs. not sure whether to ask for gluten or lactose intolerance tests, can these be done easily?
I used to get nausea with my IBS and sometimes waking nausea which was not food related . Sometimes, I would get it due to abdominal pain. You could ask for a celiac blood test and lactose test to rule these things out. Alternatively, try cutting out gluten altogether and try lactose and gluten free products before asking for any other investigations.to see if that helps with the nausea.
However, it sounds more IBS related than anything else so I would try to relax. Anxiety can also bring on nausea. Having tests can sometimes be counter productive when you have IBS because often nothing shows up and the tests themselves can cause anxiety and end up not really giving you any reassurance.