Hi there ~
I understand your concern. However, having anal sex is a high risk sexual activity in itself. I would think that any kind of douche or contraceptive
method for anal sexual activity would not be safe and carry a higher risk of infection that the usual vaginal sexual activity with penetrative sex with another individual, in this case your husband. I recommend that you visit with a gynecologist or a sexologist
to find advise regarding any potential sexual problems you may have. I hope this helps. Take care and have a lovely day!