Hand job for over an hour

I’m posting this to gain a little insight on my current situation with my partner. We’ve been dating for about 3 months. Even though I’ve had previous sexual experiences, I was never really comfortable with hand jobs, or oral whether giving or receiving it. He’s the first person I’ve felt comfortable enough to experience this with BUT I don’t enjoy doing it for that long honestly. In the beginning I do but after awhile I’m not enjoying it at all. He’ll reassure me if I tell him I no longer want to do it, but it’s an awkward tension in the air after I stop. I feel guilty that I’m not able to please him and I feel that’s it’s affecting our relationship but I can’t keep doing something I don’t enjoy doing. I guess I’m a little stuck 😐