Antibiotics causing spotting or anovulatory cycle?

[zoeh]

I was very sick for a lot of this cycle, and this morning (CD21) I just finished my last pill of the antibiotics my doctor gave me. For the past two days I've had (sorry if TMI) light brown spotting, mostly noticeable when wiping but enough to need a liner, and kind of mucus-y. It seems to be getting even lighter today. I know antibiotics can cause spotting and wacky things to happen when on oral contraceptives. Has anyone else had that happen while NOT on the pill? Or could this be a super early "period" with an anovulatory cycle? I've had a bunch of other PMS/period symptoms (tired, bloated, crampy, weepy) for the past few days but not the intense cramps I usually get the first day of a period. Even during anovulatory ones--which mine pretty much always are without fertility meds--I generally get horrible cramps the first 24 hours. Thoughts?