Setting The Stage: Jack and Jill see each other every few days, online if not IRL. They often chat, when something interests them both, and usually something does come up. They invite each other to do activities sometimes, and usually accept the offers, when they want to.
Thesis: Jack should not ask himself Do I like Jill? or Is Jill my girlfriend? and should not ask Jill Do you like me? or Why do you like me?.
Suppose Jack decides he does like Jill (romantically) -- what then? Won't he continue to do exactly what he had been doing before? And suppose he does not -- what then? Won't he continue to do exactly what he had been doing before? The same applies to girlfriend status.
Asking Why do you like me? has a bit of a different problem. Besides being useless, it forces Jill (if she answers -- she should refuse) to take a stance on what is good about Jack. Doing so can cause various problems. For example, if Jill gives reasons A, B, and C, Jack may become afraid to criticise those things about himself. Or Jack may be tempted to try and emphasise those aspects of his personality. Or Jack may become self-conscious about them. Or Jack may worry that they aren't all that good, and thus that Jill must not like him very much.
Before I close, I want to acknowledge that this isn't all completely true. Answering some of these questions can be useful for making (imprecise) long-term judgments for which the kind of approach I tend to recommend in the short-term is infeasible.