<human>: Length of relationship: almost 2.5 years

We are both introverts. I just think he is more introverted than me. If I'm just relaxing at home and I'm feeling unsocial, I still prefer only his company. Whereas with him, he sometimes prefers to be by himself. It's hurtful because sometimes I interpret it as me not being desirable enough or interesting enough for him, even though I know that's not true. 

He's my best friend and love of my life. I want to educate myself on how to be more understanding of this situation. I'm just scared of it getting to the point where he prefers his alone time more than his time with me, because what kind of a relationship would that be? I envision a future with him...if we move in together and he needs space, I'm not really sure how that would work out. 

Are there any resources out there for introversion? Could it possibly be mental illness or social anxiety or something? I have no clue. Please help.

Give me the gist of the text in a nutshell
<bot>: I want to help my boyfriend find a balance between needing space and needing a relationship. He often gets tired of people and shuts them out after a while, and that has caused a strain on our relationship.