I don’t want an open relationship

My boyfriend and I have been dating since we were 16. We broke up for a while, and got back together at 18. We’ve been together since and we are now both 20. We’re almost 2 whole years together. I thought everything was going alright. I am happy and he told me he was too. Last night, he told me he’s been having regrets of dating me from a young age. He wished he could experience more, basically sleep with others. However, he says he sees a future with me in the long run and he does want to spend the rest of his life with me. He was thinking of breaking up with me for a bit, so he could do his own thing for a while. But then he said he didn’t actually want to let go of me, and he asked to consider an open relationship for a bit. I told him I didn’t feel good about that, because I only have eyes for him. But he doesn’t seem happy with only being with me right now. I want him to be happy, but what about me? I don’t know what to say or think. He swears he loves me and that he won’t catch feelings for anyone else. He just wants to mess around. He also said he would never cheat on me. Please help.