Newly engaged

So my boyfriend and I recently got engaged. I'm 19 and he's 27. He has had plenty of relationships and he's my first. I've never wanted to be with only one person and hate that he has so much more experience than I do. I'm glad he's my first and I want him to be my last but I don't want him to be my only. But I know that that's not how things work. I would just love some advice on what I should do or how I should get over it.

P.s. He knows how I feel