Welcome to our forum.
Can I ask, how much communicating have you done with your secondary partner? If he doesn't initiate the communication, do you? When you ask him to give you a heads-up when he's not going to be online as planned (for example), what does he say?
Make sure you have communicated to him the things that are bothering you in the relationship, before giving up on the relationship. If you've already communicated your concerns to him, and he's blown them off or otherwise been poopy about it, then it's probably time to start thinking about cutting the ties with him.
That or as SchrodingersCat said, you can downgrade your expectations and not wait around for him to go online (again just using that example). Do your thing, let him do his thing, if your things happen to intersect hey great, if not no big loss. But if that isn't an option that works for you, then it's still probably time to start thinking about cutting the ties with him.
I know breaking up sucks, but sheesh, if you've been putting up with bad behavior for three years, something needs to change.
That's my viewpoint; hope it helps.
Love means never having to say, "Put down that meat cleaver!"