Hey man, I know what you mean. I have many "friends" but none of them but 2 or 3 will ever reach out to me. One from work, one being my partner and the other being an old friend.
The facts are as follows: Basically everyone is thinking for themselves, most of the time that's because they are caught up with a lot or are just distracted, it's nothing against you. You might be worried about how people think of you but they're also doing the exact same thing.
Friends is a broad term, many people you call your friends are not the same as those you rely on. If you find someone who is close to you and often call out to eachother, than that's the one you rely on. These can end suddenly tho, sometimes for reasons out of your or even their control. Don't take those that personally, it happens.
If you have close family, they're the ones you can rely on, they're blood bound. But this isn't always reliable, whether you family isn't good for you or you can't mutually hold family close like that.
There is nothing selfish about wanting to interact with people. You shouldn't be afraid to ask for someone or even to hangout with a friend group. There isn't anything annoying about being asked to hangout unless there's already something off. I'm a bit quiet at work, no one really dislikes me per se but no one really considers me close. It's a typical work relationship. However if I hear them talking about doing something like say; off-roading. It may interest me, if I had a 4 wheel drive, that'd be a reasonable point of entry for me to kind of join in and ask if I could come along. This takes a reasonable amount of confidence though and a fair acquaintance with the group. They most likely will be suggest that I am welcome. Even if it's in a cold and comedic manner. That's not weird at all. Any reasonable person would be fine with that and not think anything other than, "oh, this person likes me and wants to spend time with me."
That's not my reality though, I tend to ju.st keep to myself and do my own thing, just a personal preference.
Same goes for a "friend", hitting the up and asking if they wanna hangout is perfectly acceptable.
Also some of the best conversations are started by just doing something that is mutually interesting. It also makes a random conversation easier to have especially if it's something you know that they have an interest in.
But that's just my 2 cents worth.