my boyfriend thinks he’s gay

My boyfriend and I have been together only around 3 months. Before me though he was in a 3 year relationship with another woman. I though our relationship was going great. We’ve never fought and we get along so well. Yesterday he expressed to me that he thought he was bisexual and today he’s questioning if he might completely be gay. I 100% will support his decision if that’s how he feels, but I’m so confused and feel like it’s coming out of nowhere. I guess I should mention that he does have a problem getting off during sex and told me I was the first girl to make him cum, but he doesn’t cum every time we have sex and bc of that he’s questioning if maybe he’s not into women like he though he was. I’m kind of torn bc this is the first

guy I’ve been w who has treated me this good but I know that if he does decide he’s gay that I want to support him. It will be hard to let him go but I would want him to be happy and hope him and I can remain friends. I’m just so confused and a little heartbroken.

Edit** He told me he has never been with another man in any way. He only thinks he’s gay bc he can’t get off during sex most of the time so he thinks it would be different with a man.