It sounds like you are ambivalent about being a loner. That you feel a bit down when someone you can talk to (a friend!) is not available speaks to a need for some human contact. You say you struggle with loneliness but also note that you don't feel lonely when actually alone (and probably not having someone you would like to talk with). It is a hard place to be in. Disappointment --- I'd like to hear more about that.
As someone who had parents unable to provide emotional support, I know that I have felt that "If you don't want it, it can't be taken from you, you will not grieve it's absence"
It isn't a good solution but stepping into the feelings that have gone so long unexpressed is a scary, even dangerous, but potentially rewarding experience.