Lhasa apso shaking and panting today; been on antibiotics for 9 days. Could he just have a stomach ache?

Hi, When I came home from work today, my three-year-old lhasa apso was listless in his crate and, when I got him out, he was shaking. When I took him outside, he immediately pooped (normal) and then, shortly thereafter, pooped a second time (a little loose). He had been on antibiotics for 9 days for a skin infection. He is continuing to shake and he also yelps a little when picked up, so I think something hurts. Could this be a stomach ache from the antibiotics? Should I take him to an emergency clinic?