It might take a few attempts, but I would try to find a good therapist and work with them to figure out this state-of-being and how you can change or augment it in a way that both meets your desire to spend time alone and to resolve your loneliness. For example, maybe you need to find a specific type of life partner who also needs lots of time alone (e.g. an artist with a studio). Then you could potentially continue having stretches of alone time but with companionship during times you and your partner don't want to be alone.