That's strange. Generally speaking,I've only had such things appear when I've mixed raw and cooked(junk) foods together in quick succession. Are you perhaps eating too much in one go?
Well, if this had been me, I would have resorted to either eating some "high-meat" in order to get some extra bacteria in order to restore the right balance within my body, or I would go in for a 2-3 day-long (mineral-)water-fast to allow my stomach to sort itself out. I'm sure you're leery of "high-meat" at this stage so probably best to go for the 2nd option.
Re antibiotics:- I was once given antibiotics when I was 14. The stuff very nearly killed me, I vomited everywhere and felt like death for days. Yet, the nurse pretended that antibiotics never had such an effect. I found out later that that was nonsense.