Can thinking of an ex make him loose erection

Me and my bf broke up in january. In which he got back with his an ex.... i didnt know and we where still sleeping together for a while. (I was pregnant with our 3rd baby) when i found out he was with her i told her what was going on. Ans he lied and said i made it up she believed him and we stopped speaking for months. During this time. He would still try and hit me up at the small hours of the morning or when he was drinking. But i never bit. So when our son was born in august. We kissed. And he cried he wanted me back. I flipped. And told him to stay away from me (was still hurt by him) forward to about 3 weeks ago. We only got talking again and was caught naked together in his sisters. In which she told his gf. And they broke up. He said he wasnt happy with her. And always wanted me back. But wants to take things slow. So we started of on dates. Etc. And its been so fun so far and serious honeymoon period. Whicb they didnt have. And they had no affection. Which he loves most about me. But hes called me by her name twice already. And cancelled coming to see me last night at 6pm and didnt hear from him all night. Then today he came and got me but was off and distant. And during sex lost his erection. extremely weird for him. Would it be down to thinking about her. I did say to him this morning on the phone to leave me be if he still thinks of her.