Unfortunately some drugs take no time at all to build up in your body but take a while to leave. I don't think you're pregnant, I think the drug is still in your body.

I just had a HORRID reaction to Keflex, which I've taken and tolerated before. I was on 1,500 mgs a day and after four pills, I ended up with severe diarrhea, severe dizziness, and some stomach cramps. I stopped the meds immediately (per my doc) but its three days later and I'm still slightly dizzy.

I have to wait it out. And now the doc wants me on Clindamycin and that has crazy side effects that he swears I won't get - HA! I'm going right to the pharmacist and asking what alternatives there are that are easy on the digestive tract. Sometimes they know alternatives better than the doctor does.