Sonny is vomiting after a Urethral Obstruction

So I had another thread, but I feel that it is more important to start a new thread as this is a new symptom. Sonny vomited yesterday (it was food and therefore I was not that concerned as he has done this occasionally in the past-maybe once every 3 months.) Today he also vomited, but this time it was just mucous or stomach acid? I am now getting concerned as it has only been about a week since the urethral obstruction. I monitered his urine output and he seemed to be doing fine (small pees frequently). Anyway I had noticed he had been urinating many frequent "chunky" urines on the carpets pre urethral obstruction. I cleaned the spots up and looked tonight to see if he made anymore and did not see anything. I also felt his abdomen/bladder area and it felt ok. He yelped a little but he doesn't like me messing with him. Right now he is sitting in the spare bedroom in the basement in the dark. I'm worried about him. I have been giving the antibiotics as the vet recommended. I'm afraid he obstructed again. I will bring him into the vet tomorrow I was just wondering if anyone has had this happen before? Could it be that the antibiotics are making his stomach yucky? 

Is he still urinating normal pee? I.e not grainy