I (22F) got a friend (22M) who stutters and repeats himself constantly and I don't think he realises it

I (22F) got a friend (22M) who stutters and repeats himself constantly and I don't think he realises it I reconnected with an old friend who I haven't seen in many years, and we talk around 1-2x a week. Almost every sentence he starts he stutters like 3-5x times, and then he repeats a point maybe 2-3x times. I genuinely don't know if he realises he has a speech problem, he's doing nothing to change it, and he doesn't sound frustrated whatsoever with his speech patterns. Like no one has ever told him about it. I tried to be extremely patient, but it's starting to piss me off and I feel so bad for saying that. I even tried to say it in a nice way when he was starting another sentence, something like: "Have - have - have you tried, have you tried, have you tried to-" I cut him off saying "Hey man you should really think about what you want to say before starting a sentence because you kind of stutter and stuff like that." Then he was like "Uhhhh... ohh..." then he starts his sentence, stuttering again. I don't like to cut people off but it's been like this for 6+ months. What the hell do I do man because I think he's such a nice person to talk to but his speech patterns are killing me.