You don't say what antibiotic you're taking. Generally for dental abscesses some form of penicillin is still one of the best. For penicillin-allergic patients obviously something else must be used, and some of these such as clindamycin have a high incidence of stomach upset.

If the swelling hasn't come down that's enough reason to go back to the dentist. Sometimes it's necessary to incise the abscess to aid in drainage. Of course if you have some unrelated bug it's just going to make you feel even worse, and an infection tends to decrease your resistance to catching whatever bug is going around. So if your dentist feels the tooth is getting under control, it's still a good idea to chech with your physician.

Good luck,

Steve Bornfeld, DDS