That's not how it works at all. Read the studies again. You feel affectionate after sex but those hormones don't last more than a day. Sex alone doesn't make you love someone, especially if it was a one night thing. Nothing about having many partners makes you unable to love one person, it's that people who have many casual relationships can't/don't want to bond in the first place. Chose your sexual life with your values and needs instead of inventing facts that don't exist