BF saying no to sex

Me and my BF have been together for almost 8 months. Last month I confronted him for me finding a convo between him and a girl from his past. He was saying how he was single and how he had pics of her (which he really didn't but you could tell they sent each other pics.) He deleted the girl and he hasn't talked to any girl since. Since then he's watched a lot of porn and keeps saying how he's gonna have sex with me so hard but by the time we go to bed he tells me no. Same thing in the morning. We used to have sex like every night. Now it's super rare. I'm tired of being turned down and feeling like I'm doing something wrong or like the sex is terrible. He tells me it's not bad but I just feel like something has changed as if he isn't as attracted. Has anyone else had this problem or felt this way?