I'm on phentermine for nearly a month. (Duromine 30mg). I am not overweight (bmi 19) but just wants to lose some weight. I know it's dangerous and illegal, but never mind that. I didn't take it everyday, but one every 3 days to keep my binge habits at bay.
I didn't experience much side effects other than dry mouth and feeling more energized. However I do realised my bowel movements were affected.
I usually have irregular bowel shapes/sizes (before on phentermine), can range from having diarrhea today and constipation the next. But I do pass motion everyday, sometimes twice, sometimes thrice.

I realised after taking phentermine, I have stomach pain, it's sudden and mild, doesn't last long, but it can range from the left to right upper abdomen to lower abdomen pain, basically anywhere. I'm thinking it could be possibly gas pain. Since I noticed I've burp and fart a lot after phentermine consumption.
But what's bothering me is that I had a hard time passing motion after I'm on the drug, and I'm worried I might develop hemorrhoid due to constant straining to pass motion. I increased my fibre intake, I realised it helps, instead of poops that break into pieces, I managed to poop a whole now, but I realised some yellow spots on the poop? The colour is normal light brown. But these spots are freaking me out.

Is there any possibility that phentermine causes stomach ulcers or any gastro issues?

Oh I do take naproxen with famotidine every month during my period. But only I tablet on the first day.

I do have gastric/gallbladder pain every now and then wayyy before I started phentermine. Probably been a few years, but it is v mild and doesn't really bother me.

Sorry for the long post. Would gladly appreciate any profession's reply. Thank you