How to let this guy know I'm interested? (I'm an aspie) help?!?!?!?

Ok so first off I have Asperger's syndrome and I'm female. Second l really like my friend and I have a feeling he might like me as well. So anyways I feel like he thinks I'm not interested in him because it's kinda weird when we talk because sometimes I'm not sure how to respond to him. So I basically have no clue whatsoever how to start a conversation and I'm not really good at keeping them going either. He thinks I'm not paying attention to me whenever he talks to me (he told me that) and it kind of seems like I'm not very opinion oriented because I'll usually just say "I don't care" or I'll agree with whatever he says because I get nervous and embarrassed. And I have no clue how to flirt or show him I like him. I have tried in the past with other guys and I only came across as creepy and scared them haha. So anyways any help would be appreciated. I'm 21 so it's kind of important as conversating and flirting are things that "normal" people my age are expected to know how to do.