confused!

I'm 18 and I've only been with one guy. He wants to get married when we're financially stable, and I want to also. The problem is that I want to have more experience. I want to know what it's like to be with a different guy, but my boyfriend doesn't want me to be with another guy(who would blame him). I don't want to breakup with my boyfriend just so I can see what other guys are like, but I also know that if I do marry him with out having other experiences, I'm going to regret never trying anything with anyone else. 
I don't even necessarily need to hop on another guy. I want to know what it's like to kiss someone else. I want to know what it's like to go on a date with someone else. 
I don't know what to do 😩😩😩😩😩
Edit: we aren't planning to get married soon at all. We're planning for 4-6 ish years from now. 
I have told him how I feel, but he told me he doesn't mind that I feel that way, but he will mind if I act I that feeling.