How can i avoid pain and leaking after anal sex?

Not good: This suggests mucosal damage. This can substantially increase your risk of HIV / other std if not using condoms. Should give it a few days rest, then resume w/good lube & condoms (always). If constipated, you may be contributing to problem--consider stool softener (miralax (polyethylene glycol) / fiber gummies / prunes -- whatever you can take reliably). Steroid hemorrohid cream might help also.