what i worry about if he’s dating multiple people…
like his roommate is, my co-worker. how do i know when he’s
serious about me? when do i know i can start investing in
him?…i don’t know what the signs are anymore.

anyone care to answer her?

Not like I’m at all qualified to give advice with my trainwreck of a personal life, but I think a good rule is that if someone is dating “multiple people” and they’re actually telling you about it, that’s equivalent to them saying, “Don’t invest in me.”