Objectively, how would you advise a friend if she told you this?
I'm just struggling to understand what it means when someone has time to be online, talk to friends, and like your stories, but not send a simple "hey" to their girlfriend for 5 days
No you're not. Deep down, you know what it means, but understandably, you don't want to accept it and you're frustrated, looking for other explanations to explain this behaviour.
Despite what he's telling you, he's just not that into you. He thinks you are permanently available for him when he can be bothered to communicate, when he's bored, lonely or horny. It's quite an asymmetrical situation, don't you think? I also wouldn't count on him seeing himself in a monogamous relationship, rather, you are someone he just keeps on the side for convenience.
He is communicating with you with his actions, and his actions are he just doesn't have the same needs as you, or you are simply not a priority for him. When he views his stories, it's not that he's truly interested in you. He just wants to keep an eye on you to make sure you're not drifting away from him (because that would not be convenient for him).
I want you to remember this ok? Very often, if you're confused about someone's behaviour, it's because they're not that into you and / or they're a users. That goes for friendships as well btw.
They will breadcrumb you in order to give you just enough to keep you hanging on. They may be charming, polite in other ways, enjoyable to be around....but they're still a user. They will lie to you to keep you committed and available.
If you start withdrawing, they may have a little panic and try to stuck you back in. They may seem genuinely distressed when you tell them it's over, but that is not them caring about you. That is them feeling a sense of abandonment. There is a difference.