I've been getting bouts of nausea, it's triggered at various times however most commonly (though not always) when I'm going to eat.

I haven't yet seen a psychologist about it, though I have been to a doctor and it has been confirmed that they cannot find anything wrong with my stomach.

What I assume is that it's some form of anxiety, where when I'm nervous I make myself feel nauseous/feel like I'm going to throw up. I haven't yet been sick which also makes me think it's psychological. It most commonly happens when I'm going out and when I'm about to eat.. I can generally still go out when this happens, however it rather difficult for me to eat when I feel I'm going to throw up. To an extent I think it's a self-fulfilling prophecy, I think I'm going to be sick, which makes me anxious, thus I feel sick.
It's been going on for a while but it comes and goes.

Has anyone else had this problem, or have some suggestions? I don't want to get in a habit of not/hardly eating because of this.