Help please! Is my 25 year old son autistic?

I would really welcome any advice members can give. I am finding this very hard.

I have a 25 year old son , who is high functioning in many respects. He got through school fine, did well at University , is living independently and appears 'normal' in terms of social communication, friendships etc.. There were none of the obvious signs until now that he might be autistic to the outside world (other than my intuition). He had a good group of friends at Uni. school , has hosted radio shows etc and even has a degree in communications.

however , I strongly suspect he is on the autism spectrum (my father , now deceased, was definately on the spectrum and I believe my brother is too). I have been worried about my son for years - difficulty learning new material at school, very rigid patterns of thinking, obsessive hobbies, wanting complete clarity in everything he does, an inability to read social cues outside formal situations , stress when faced with any uncertainty, sensory issues etc, no girlfriends yet despite expressing an interest in having one). The problem is getting more serious now though as he was let go in his last job  , for no apparent reason, but reading between the lines it may be because of him displaying these traits in a work situation. After a short period of unemployment, he was hired to a great , new job, at management level. Within a few weeks he is underperforming and his new boss has said she may have to let him go - again, listening to what his boss said, it sounds like it could be his rigidity and lack of understanding of how to behave causing this. I have tried to gently mention to him perhaps he needs a particular environment and could perhaps be on the high functioning end of the autism spectrum (which would not be a problem, but helpful for self awareness and to choose the right work environment in future) - but he is strongly resistant to this. His self image is important to him, and he seeks adult independence. He is convinced the problem is his boss/ the workplace / colleagues and is not ready to consider his own behaviour might be behind this inability to fit in. He has said he intends to find another similar job in a slightly different field! He had a childhood friend with autism who went to a specialist school and he has a negative view of what being autistic might mean. I am really worried now as he is incredibly stressed at work, and I think is about to be sacked again. His savings are dwindling and he is so frustrated with trying to find a job he enjoys. He works very hard too.

At the moment, I think it very unlikely he will request a diagnosis or seriously consider whether he might be autistic. How can I help him come to terms with his situation, and help him establish a good independent life if he is not diagnosed?  (By the way, I am a /was a career coach by profession, so could help him through employment choices!). How might I convince him to get assessed? What services might be available to us as his parents to learn how to help him manage his condition and also our own emotional reaction ? he relies very heavily on our day to day advice and support, and financial help, and we are feeling like things are never going to improve. (We are prepared to pay for specialist help if needed). Really appreciate any help from others who have experienced a diagnosis of an adult child. Thankyou

Lisa