How can I help him?

I would guess that he sees himself in this situation as unfit as boyfriend material for you. 

The pieces don't seem to fit. 

People with asperger, like me, we don't take the emotional side of a relationship into the equation. It doesn't come as self-evident that being there to listen to your partner actually has real value. 

What can also be an important factor is fear for being exposed as incompetent and then losing control over the things you planned to do. I had a situation with my brother-in-law where he snatched a rake out of my hands to show me how the gardening-job is really done. That hurt me, I started to think what signals I must send out to other people. Although the evidence always shows that I get the job done in the end. 

You could communicate this to him: you need hugs, they have a value for you, you don't want hugs for free, you want to return the favour, you're in a relationship, that usually means task-divisions, a tip: usually phonecalls are like roadblocks for people with aspergers, that could be something you do for him, but make it very clear that you're not planning to take it all over and solve problems for him. 

Thank you. Yes that does make sense. He has said a few comments before suggesting he isn't good enough. He always gets back in touch when things are sorted and he is back to 'normal', i.e functioning properly again 

If it's possible for you to get hope from the good things that are, and not hope that things will change a lot, you could have a nice relationship, but it's always going to be a bit strange.

I read here also from you that his family thinks he's selfish. That doesn't seem to match up with the fact that he was reluctant to borrow your car, and didn't take it for granted. It could be that he told them a couple of times that he had enough problems to deal with and he's not able to help others right now. 

I'm married, I have a daughter of 18 and a son of 15, full time employment, own house... so if people tell you it's impossible to have a working relationship with somebody with autism, it seems it can be done, but I don't think my wife always has it easy with some of my quirks. 

Direct sentenses in communication, calmly discussing issues, stating what you want, what you expect from the relationship, make it clear, don't expect him to take a hint, we don't do well with subtext.

Emotions are also not our strong point, we get confused by them, if you want hugs, more likely you'll get hugs if you make it clear that you like hugs and you need them a lot.  

He does so much for his family, he is at his happiest when helping people. He cooks for them all the time, does free work around their house, fixes their cars etc. But they misunderstand a lot of his actions as him not caring. E.g he walks out of arguments rather than helping/supporting them. Or if he sees his mum crying he leaves the house. They interpret this as him not caring when they dont see he just cant cope with seeing any conflict or others upset due to his aspergers. And in fact he is leaving the situation because he cares too much and cant handle the emotion so he knows he needs to leave for his own good. Also because he wont just 'man up' and get over his issues, manage his debts and turn up in court etc. They dont understand it's not that simple for him. 

I can see a relationship working with him very well. I am lucky that I understand him and can be patient. There is still a lot I dont quite understand and I'm working more out slowly. He just struggles to communicate with me when he is needing help and doesnt explain how he wants me to approach things which is why I thought I would ask on here. Thank you for all your help

He does so much for his family, he is at his happiest when helping people. He cooks for them all the time, does free work around their house, fixes their cars etc. But they misunderstand a lot of his actions as him not caring. E.g he walks out of arguments rather than helping/supporting them. Or if he sees his mum crying he leaves the house. They interpret this as him not caring when they dont see he just cant cope with seeing any conflict or others upset due to his aspergers. And in fact he is leaving the situation because he cares too much and cant handle the emotion so he knows he needs to leave for his own good. Also because he wont just 'man up' and get over his issues, manage his debts and turn up in court etc. They dont understand it's not that simple for him. 

I can see a relationship working with him very well. I am lucky that I understand him and can be patient. There is still a lot I dont quite understand and I'm working more out slowly. He just struggles to communicate with me when he is needing help and doesnt explain how he wants me to approach things which is why I thought I would ask on here. Thank you for all your help

Direct sentenses in communication, calmly discussing issues, stating what you want, what you expect from the relationship, make it clear, don't expect him to take a hint, we don't do well with subtext.

Emotions are also not our strong point, we get confused by them, if you want hugs, more likely you'll get hugs if you make it clear that you like hugs and you need them a lot.