Three years isn’t bad at all I don’t think, as long as both partners are emotionally mature but that goes for any relationship really even if you’re the same age. I’ve dated guys 3-4 years older than me but they were very emotionally detached and it was no bueno so wouldn’t recommend that but if he treats you right then I don’t see the issue tbh. After all, age is just a number. Hell, I think my grandparents were almost 10 years apart and they were together for 50 years.