Thank you for the query.
Anal abscess does not appear without the reason. Usually it is a symptom of rectal fistula
. According to your symptoms, you may suffer from some kind of inflammatory intestines disease (Crohn`s disease). This disease can give diarrhea and constipations alternately, as well as the blood in stool
It is possible that your symptoms can be also caused by intestines infection due to antibiotics therapy (pseudomembranous enterocolitis
It is strongly advisable for you to do not neglect such symptoms. You should have colonoscopy
performed and stool tests if no findings in colonoscopy.
Hope this will help.