Alarm bells ringing... I think my husband has ADHD?

Apologies for the lengthy diatribe but this is 25 years worth... My husband and I have been together for a long time... 25 years (married for 11) but for almost all of that time I have felt frustrated and let down by him in so many ways. On the outside he's a nice guy... gentle, funny, easy going, never mean or argumentative with other people etc. but even when I first met him he was sort of in his own little world, obsessed with cars, a bit OCD - always cleaning certain things - wiping down kitchen cupboards or polishing the car to within an inch of its life - but oblivious to other things like clean sheets, clean bathroom, dishes in the sink, decent furniture etc etc. He was also always late and had a reputation for tardiness with his friends. He was the laughing stock and thought of as a bit of a hopeless case but we were young and he was cute and so I fell for him. He was also a talented graphic designer (loves details) and had a good job so I figured all would be well. Back then he was affectionate, even tempered (unless I pushed him out of his comfort zone or tried to get between him and his cars), kind and even generous in the beginning but he was also thoughtless, forgetful, disorganised, late, and would never call. He was dismissive of my feelings at times but very apologetic at others and constantly promised to try harder but rarely followed through. It was like he wanted to be the man I needed him to be but he didn’t know how. It caused a lot of fights when we were young, but we were young and I thought he just needed to “grow up” so I waited and nagged and sucked it up and surrounded ourselves with friends and activities and work, and life went on. Over the years, I have tried to accept his rituals, obsessions, lack of “class” or romance, forgetfulness, disconnection etc and sort of grew into becoming his pseudo mother but it has destroyed me. I slowly took on more and more responsibilities and have pretty much always been the driver in our life - prompting and organising everything from social outings to purchasing of property, furniture, equipment, holidays, marriage, children and most recently a new business, while he has been the passenger. His own mother was mentally ill and his father left when he was very young so I have always felt very sorry for him as he had a tough upbringing and I thought his self centredness and need to keep his world focussed was all due to this. Fast forward 25 years and I am BURNT OUT… We now have two children, a mortgage, two businesses ( I have my own and I help him with his as I always feel like it’s going to fall in a hole if I don’t) and I feel like I doing more than ever before. He is a good, fun dad to the kids and he works hard (although not very efficiently) but he’s completely disconnected from me – even though he doesn’t think so. Oh, he’s still affectionate (except that I don’t let him near me) and tries to crack jokes (which are not funny to me any more) and likes to get take away food and a movie at 9pm at night (after he comes home 3 hours late with no phone call), but he is mostly oblivious to my feelings and remains in his own little world where mummy here looks after everything. He is not a mean person and I honestly don’t think he does things maliciously but there have been so many incidences where he has let me down (not doing the one thing I asked him to do on our wedding day, spending the day after I gave birth looking for a new car instead of visiting me in hospital, watching the TV in hospital and eating my hospital dinner because I was so distraught about our new born’s health, poking fun at my anxiety about our daughter’s illness, secretly sending $2000 to buy a go-kart when we were struggling to stay afloat, buying a new motorbike without telling me, forgetting Mothers days, anniversaries, birthdays etc, rarely organising date night (despite repeated hints, promises, meltdowns), taking no interest in Christmas presents for the kids or his family, never organising family outings, taking no interest in kids’ education, sporting pursuits etc,, leaving renovation to me, leaving all bills, tax, cooking, social events, shopping, etc etc to me) that I feel like there is a black pit of anger and resentment that I just can’t get over it. We had another “talk” about it last week when he came home 3 hours late after telling me he'd be 20 minutes and I gave him an ultimatum (again) and then the benefit of the doubt (again) because he was upset, sorry, down trodden and confused but two days later he let me down again in a big way and that was the final straw. I suddenly realised that he will NEVER EVER change and I feel like leaving but I am trapped. So at the moment I am punishing him again by being mean and silent with him and that is just killing all of us. I thought he might have Asperger’s but perhaps it is ADHD. What should I do? Where do I begin?