Can I have anal sex if I have proctitis?

You shouldn't. Proctitis, even in remission, might be exacerbated or actived by recurrent anal trauma. Certainly not if active, symptomtic proctitis is present.
No. I would not recommend that. Anal sex may traumatize the area which is already diseased. You need to ask this ques to the doctor who is treating your proctits, either a GI or colorectal surgeon. Only they know the severity of tour proctitis and can advise you accordingly.

Related Questions

I'm an asymptomatic carrier of salmonella typhi after traveling. Am I at high risk for bacteremia or proctitis if I have anal sex?

Probably not, but... ... you probably shouldn't be having anal sex all (and perhaps not vaginal sex), at least not with new partners, until this problem is gone. If you have a regular partner who is aware of the risk, that should be OK, but you must not put new or unknowing partners at risk. Condoms probably would only partly reduce the risk. But probably no risk for you. See an infectious diseases specialist. Read more...