cpietra, we have 3 spayed females, all with spay incontinence. In all three cases, the onset was sudden. So if the antibiotics do not clear up the problem, it may still turn out to be spay incontinence. Sudden onset doesn't rule it out.
There are two different meds that can be tried for incontinence--one is the DES (estrogen) that has been mentioned, and the other is pheylpropanolamine (PPA). Because of the risks of long-term use of estrogens and the fact that the first two of our girls that became incontinent pretty much needed the meds every day with no breaks, we opted for the PPA. Belle has been on it for some 4 years with no problems.
I hope she's better soon
I know how worrisome it can be...