I have kidney stones & uti, plus uc! Need help

I am a long time Healing Well patron, I've been doing well until I got kidney stones. My uro dr. has put in a stint to help while I fight a uti. He prescribed keflex 3/day; my gastro dr. addedd flagyl to take with the keflex plus yogurt 2x/day. I'm also on a regimen of 4 mesalamine/day and humira 2x/mo. both for the uc.
Now having diarrehea after meals (small meals) so I'm taking immodium for that. Can anyone tell me why 2 antibiotics?

will be calling the uro dr in the a .m.

Thanks for clearing that up for me. I pray I don't get cdiff. I've had that and the way to stop it and clear it up ain't pretty. Wonder if I should take fiber capsules...I take so many meds and supps I hate the thought of adding more.