Not always, but some people have a hard time
taking them. You absolutely can not drink alcohol
while on
metronidazole. It will make you very ill. If you end up taking it (you shouldn't), don't drink alcohol for at least 3 days after your last dose.
You really need to get a hold on your anxiety. I don't know if you cheated on a regular partner and that's why you are so anxious, but guilt does not equal risk.
Get counseling.