I've read that the worst effect was stomach cramps and diarrea. Stop taking the tetracycline and both problems went away by themselves.
I took a course of tetracycline many years ago and had non-stop diarrhea the entire time, and for 5 weeks after. I mean like 10 times a day.
Finally had to go to an acupuncturist to cure it.
I have bad to extremely bad reactions to most pharm meds I’ve taken. That’s one reason I became an herbalist.