Need opinions

So my boyfriend and I have been in a relationship for 4 months, and everything’s going great. We’re so into each other and love each other, we have fun together, like the same things, and want the same things. Since our first date, we’ve just clicked and have amazing chemistry. But the other day, he almost broke up with me because he started to get worried that because things were going so well, he could see us settling down together and having a future. I should probably note that he’s 21 and I was his first date, kiss, girlfriend, and first person he’s had sex with. I also was not his type when we met. I’m a little on the curvier side and he was into the more “traditional” idea of a hot girl. Anyway, he almost broke up with me because he was scared that he’d never get to experience sex with another person, and was afraid that years and years from now he may regret never being with anyone else, and would worry if he was with me because of his love for me, or because I was his first and it was easy being together. He broke down into tears as he tried to communicate this with me and when I asked if that was the only reason he was breaking up with me, he said yes. That he absolutely loves and adores me, but wants to choose me knowing what else was out there, and that that wasn’t fair to me. I then suggested a “hall pass” situation where he’s allowed to have meaningless sex with someone just to see what it’s like and get it out of his system, and we could continue our relationship. He said he has no desire to get to know or “date” someone else, just to sleep with someone more his type so he could know what it’s like. He said he wouldn’t seek anything out, but just wanted the fact that if he was out with his friends at a club or something and the opportunity presented itself, he could act on it. That’s why he was breaking up with me. After setting some ground rules such as once and done, no contact info, no kissing, he has to tell me when it happens that it happened without any detail, and not in his house. We agreed to continue our relationship knowing this could possibly happen a few months down the line. I’m just wondering, is this a mistake to do? I completely see his point of view and had done something similar when I first started dating, but at the same time it hurts a little to know he physically wants someone else and feel like I’m not enough (which he adamantly tried to tell me wasn’t true, that he’s so beyond happy with me in every way, especially sexually)