Can i get an ibs flare up from taking amoxicillin?

One expected effect of taking any oral antibiotic is it will kill off many of the susceptible gut germs, leaving the remaining germs and yeast extra room to flourish. While this would not cause a problem for most, those with IBS may experience a change from baseline. Taking probiotics during and after antibiotic treatment can re-populate the gut with favorable germ strains & counter this effect.

Yes, as previously explained and more as antibiotic induced diarrhea and C diff colitis are increasingly seen complications of antibiotic therapy.