Welcome to healthcare magic!
It seems like you have some local problem at your anus and rectum
It is unusual to have pain/fungal infection
after stopping antibiotics if you did not have any problem earlier when actually taking them.
If you have a tight motions-hard stools, then taking Susp. Cremaffin
would help a lot.
Still I would suggest an physical examination by your surgeon and get base line investigations like Complete Blood Counts, Renal Function Test, Ultrasound
Abdomen, Urine Compete Examination.
This work up is expected to detect the underlying problem so a definite treatment could be started.
I hope this advise would be helpful for you.
Still if you have any queries or doubts, please write me back,
I would be happy to solve them.
Wish you a great health!