Well, for me I have always (since I was about 16 or so) felt that there was "something" - I always had this feeling that it wasn't supposed to be this hard, wondering why I couldn't just manage ordinary things. But just kept putting it down to various things - hormones/wrong college environment/pregnancy/newborn/emotionally abusive relationship/single parenthood/vitamin deficiency. Eventually I came back around to depression because I realised that the common denominator in all of this was... me. But I was confused because I was happy most of the time. I had counselling four times and it never gave me any huge insight or found it really very helpful. In fact, the counsellors usually ended up "sacking" me because they'd say they didn't know what I was there for. I have always been quite eloquent about what my problem is and quite aware of what I needed to put in place to fix it, the problem was that I just wouldn't put the thing in place, and then I'd get really frustrated with myself.
I think it was about 2013 when I was really trying to get a handle on myself again and trying the 1000th self help strategy again and still ending up crying on the kitchen floor in the middle of the night because I just didn't know why it was so hard and feeling a total and utter failure as a person. I'd managed to pull together every issue I was struggling with and write them into a list (I had several MN threads, over the preceding years, where I was like "Right I've got to sort this out now...") and one day I came across the list of Inattentive ADHD symptoms and was like "Oh fuck that's me. That's my list."
I don't know, for me it really HAS had a huge measurable effect on my life, if I look back, it cost me those three separate study efforts, my house was so messy at one point that I had both social services and my landlord on my back, it really was that bad. I got into loads of debt by not reading letters and not submitting correct forms (in one case I filled the form in and simply never posted it). I've never actually had what I'd think of as a "proper job" for various reasons which all boil down to: ADHD. I've never been fired from a job, but I've had warnings at all of them. I once killed two gerbils
by forgetting to feed them. :( I had a teenage pregnancy (albeit in a controlling relationship). I do OK now. But I would have said up until the last 2-3 years, I couldn't have coped with running a household on my own. Even now I think I'm hugely scaffolded by my DH and he is fantastic. I don't know what I would do without him.
But having said that I know people do get through university and careers and yet still have ADHD. Perhaps you had better coping mechanisms than me at that stage, or perhaps you had a different family situation? I do think if I'd been in a family where everyone had been to uni and had a career, that's probably what I would have ended up doing. I would have done A Levels rather than art college and at sixth form I probably would have absolutely thrived, especially if I'd moved schools at that point. My mum is brilliant and was all for me following my dream of art but actually looking at my grades I was never that good at art, design yes - I should have gone into maths or science, and from there into something along the lines of product design/development or market research and statistics. I think I would have been fantastic at that, and I have a slight suspicion that art was a more "feminine" choice for my mum, because it was creative, and so she probably supported that more than she'd have known how to push me towards STEM. And I had no idea about careers or how to look for jobs, no idea how maths or science would have related to anything that I would have found interesting long term, and it's only really now (as in, literally, this week, and I honestly think maybe relating to clearer medicated thinking) that I've really had any idea of where I ought to start looking for jobs where any kind of education is really needed because NOBODY that my family knows has a job like that. And I think if I'd had that knowledge back when I was 16 I probably could have quite easily found myself funnelled down a much more productive or helpful path, rather than drop out > flounder > drop out > baby > flounder > drop out > flounder, because I need that external structure and it was only clear to me what I was supposed to do up until the age of 16.
I've gone a bit off topic, but yes, everybody procrastinates, everyone is secretly a bit messy and disgusting, everyone struggles to keep up good habits, everyone is lazy sometimes when they know they shouldn't be - my baseline for whether somebody should go for diagnosis is - can you control it? Can you actually get going if you kick yourself up the arse? Because if you can then you probably don't have ADHD. OTOH if you are exhausted trying to kick yourself just to do the most basic of things and it still isn't working, that's not normal, if you don't feel in control of it, it's not normal. If your inability to deal with this stuff is leaving you in despair that is NOT NORMAL and it's absolutely reasonable to present this situation to a doctor and say "I don't think this is normal, please help me".
Subtypes: If it helps then go with it. As far as I know clinically they are still used, certainly my official diagnosis has it and so does DS1's which is only from last year. We are both inattentive. Dr. Barkley is an outlier saying they should be scrapped but I do hold him in higher esteem personally than most of the literature about ADHD. Just be careful with info online and in books - some of it crosses into cod psychology. But yes broadly - inattentive type - you have more issues with focus, concentration and organisation - hyperactive type people have more issues with impulse control (perhaps illegal/unhealthy behaviours), emotional control (esp antisocial stuff - aggression/mania), combined type experience both. That's the diagnostic criteria. As with anything though I think you need to take what works for you and do what you need to do with it, if that makes sense?
I really liked the book "So I'm not crazy, stupid or lazy?" - it's a bit outdated now but a great intro to ADHD especially for women.