Sorry to hear about your bad experience utk1976. I don't know how long prior to your lunch you popped the caps and I'm not sure what the serving size is but the bottles of 5-HTP that I use have a serving size of 1 cap only so if you didn't stick with the serving size, you should.
Aside from that, you can try taking your serving during a meal and see how it settles on your stomach.

I've taken 5-htp on an empty stomach before and it didn't settle too well lol. Only thing is that it came out thru the backway, not my mouth lol
I don't know if it was a chemical reaction between the 5-htp and your anti-depressants but I would try the above if it concerns you.