May I gently poke at you a bit? (gonna anyway!) You’re thinking of depression as you think depression should show up for you (down, bummed, blue, whatever) and it can take a totally different form than you think! Because you don’t recognize it doesn’t mean much really.
I’ve been sick for four years now with my thyroid levels normal (euthyroid eye disease) and my new doc insisted I go on antidepressants mostly for the sickness, aches & pains, etc and by golly, I think he may be right!
Do get your tummy checked out tho, but keep open to the possibilities.