Could my quirky depressed son be Autistic?

Hello, Im new here and looking for advice.  My 19 year old son has been suffering with depresion for 3 year on and off.  He was a well behaved child did well at school, passed his GCSEs although I was slighty disappointed with his C grades as thought he was capeable of better.  He went to college and started working at McDonalds part time.  He left both college and McDonalds after telling us he was depressed, he has been seeing a councilor who he really liked and started taking antidepressents, he did a 12 month apprenticeship and has gained a full time job from it, we were really pleased with his progress.

He weaned himself off his antidepressents in the summer and he has been low since.  He talks to me a lot and was saying how he doesnt fit in with his current friends or anyone else for that matter,. This weekend he hit rock bottom, he refused an invitation to a party on friday and wouldnt go to a football match on Saturday, because he felt so low.  He always says that nothing interests him, he doesnt relate to people his age and is not interested in girls in the slightest, they get on his nerves and doesnt get the whole relationship thing.  I have thought he may be gay in the past and have asked him, he says he isnt.  He is quirky and was as a child but nothing really that noticable, he is sociable and can make conversation with people, escpecially good with older adults, he has a very dry sense of humour and can be really funny, I have heard others say that too.   He tends to get a bit obsessed with a subject and keeps talking about it, he likes to analyse people and himself a lot and doesnt understand if they think or behave differently to him. He has always been a terrible fussy eater and hasnt improved much as he has grown up.

On Friday I started watching Aspergers videos made by young people on facebook and I have now convinced he is on the spectrum, but I dont know what to do?  Will it help or make him feel worse if I mention it to him?  We watch The Undateables and see young autistic people on there, but he looks at them as being disabled certainly nothing like himself , we also had a 'weird' nieghbour lodging next door who had aspergers and killed the landlords cat! I am hoping I dont offend anyone on here by saying that, but I am just trying to explain how I think my son will look at it.

I am quite knowledgeable on Aspergers now as I have done nothing but research it all weekend. There are lots of other little traits that he has that I have picked up over the weekend.  If it wasnt for the depression I dont think I would say anything to him about it, but I just dont know what to do?  Any advice or experience would be appreciated x