My bf cant stay off porn sites

My bf bought me a promise ring made all these promises then i go through his phone and see hes been video chatting on porn sites idk what kind i was upset i told him we were done. He leaves flowers on my car and letters so i take him back and he said it would never happen again but not even 3 weeks later i find it again in his phone and his excuse was i dant help myself idk y i do it i didnt think yu would even check again, he gave me the tears and all the boohoing but idk hes not physically cheating but cant trust a liar right