Casual sex..catching feelings???

I’ve been having casual sex with the same guy for about a few months now. From November to now. Before, we could have sex and I didn’t feel a thing for him. But, We just had sex last night and I’m realizing I’m starting to catch feelings. He’s such a gentleman and after sex, he always asks me to sleepover and we cuddle the entire night. Last night we even shared the same pillow. Sometimes I have to remind myself he’s not mine. We’re not together. And that hurts. Because before I had sex I talked down on casual sex. Now that I’m doing it I feel like its okay, but I’m sharing a part of myself so intimately with someone that I can’t help but to grow feelings for them. I don’t want it to be like this because I know we’re both young, I’m 18 and he’s 23 and he doesn’t want a relationship right now. And I don’t want to make this awkward between us. I enjoy sex with him, and we are very open with communication when it comes to things we like during our sexual encounters. But how do I stop myself from catching feelings so my feelings don’t become stronger every time we have sex?