There are two modes of dating multiple people.
Mode 1 is like an interview phase of a job hunt. You date a bunch of people, second date some proportion of them, third date a few, and either then cut off the rest, or stop seeing that person. There's no dating on and on and on with someone, after a couple dates either you're settling in with them, or not. You probably don't fuck them till you stop seeing others, but you might fool around.
Mode 2, you long term date and fuck a handful of people, and occasionally one ends, and occasionally you add new people to the mix.
If you're a mode 1 girl, you can go on another date with this guy if you can see him potentially being your monogamous boyfriend, you don't see him again if not. If he's still 'maybe' you keep dating him and others, but not for that long. If you're wanting to fool around with other guys but not him, then stop seeing him.
If you're a mode 2 girl, you keep dating him if you want to fuck him if things keep going well, and you don't if you don't.