That's the trick, isn't it. I think had I got a diagnosis as a child, I'd maybe have been better equipped to handle socialising through school and uni, rather than trying to initiate closeness but not being able to recognise and act appropriately on the responses, and having my attempts ending up in horrific bullying, sexual assault, depression/alcohol abuse/self harm/suicide attempts all by the age of 21. I don't know how usual this is, but out of my siblings (2, I'm the oldest), I'm the only one who has had no contact with anyone from school since leaving school, and I only keep in semi-regular contact with two people from uni (both flatmates, who I didn't have to seek out, if that makes sense). I keep no contact with any of my former work colleagues. If a friendship presents a challenge that I wasn't expecting, my default reaction is to just retreat into myself and panic. DH and my siblings all keep in contact with people they've known almost their whole lives.
I have friends on Facebook who I met through antenatal groups who all chat amongst themselves, and I've wondered if I should message some of the ones who have spoken to me separately in the past to apologise for if I've come across as though I'm not bothered for their friendship, when I am, I just don't want to impose on their lives, or have them thinking "Oh fgs not her again". Same with my uni flatmate who's recently had her first child - I don't want her to think I'm bothering her, and I've been having to try really hard to not message her lots to ask how she's doing, how the baby is, or send presents for the baby because I was so happy that this person who I really care for has this wonderful new thing going on in her life.
Sorry for the verbal (or typographical :P) diarrhoea there... I don't tend to commit these thoughts to words.