Dealing with Nausea and Anxiety: Need Advice

I've been having nausea on and off for a while now. I initially thought that it was as a result of a previously ignored dairy intolerance until it started up again this week despite not having had any dairy for over a month. I've also been eating a lot less due to anxiety. I have no appetite and really only eat out of habit (like breakfast) or when my stomach starts growling or something. I otherwise have no motivation to eat, especially now that I can't have dairy. So now I don't know I'd the nausea is because of another ignored food intolerance (Gluten), not eating enough, or if I'm just sick. Or maybe some combination of some or all of those. Has anyone else had similar problems with any of these things? What can I do to make myself eat more even if it makes me feel sick? I need to work on that reguardles of whether or not it's the problem...