The main symptoms of ADHD have been present in me from the age of 3, my 'parents have noticed it, teachers in school and college noticed it and my friends can also verify it.

Looking in the DSM-V, it has to be present in 2 or more settings, and it affects every are of my life so that's a yes.
I have severe concentration difficulties, I am a very bad (not so extreme anymore) procrastinator, I have very bad short-term memory, I am extremely impulsive and am highly hyperactive.

I know the condition is far more complex than going down a list of symptoms and characteristics and saying I have something based on that, but people who are trained to spot things in children mentioned many times I should possibly be tested for ADHD during school and college, and I meet every single characteristic in the DSM-V to a very high degree and always have.

Now I work and it is affecting me very badly there as well. In a warehouse with forklift trucks is dangerous because I nearly get run down countless times because I lack focus when picking and packing, even if they press the horn directly behind me and people shout to me to move it takes me a while to hear them because I'm so absent-mindedly doing work.
I also make tonnes of really stupid, careless mistakes (sounds like my entire life in one sentence. Haha) and am constantly getting shouted at because they think I do it on purpose. I try incredibly hard to pay attention, I even meditate which does help a lot but because my concentration and inattention has always been severe it hasn't noticeably improved as of yet to anyone but myself (but I expect it'll take years of mediation for other people who aren't in my head to notice).

Here is the thing...I cannot say anything because I technically have no diagnosis of anything, not even ADHD, so all I can do is put up with the moaning from them and make up random excuses off the top of my head even though I don't know how else to explain it other than I have poor concentration and very, very short attention span (except when hyper-focusing but I have never learned how to consciously control that).

Is there absolutely any way, any at all, (I'm planning on going to get tested sometime this year, somehow, hopefully) I can tell them I potentially have undiagnosed adult ADHD and use that as a valid reason and not an excuse? I would rather not use it as an excuse (or reason) but some people only understand something when you have a label unfortunately, especially in the workplace.

Thanks. Peace.

EDIT: here is my response from the ADHD screening test on this forum:

Based upon your responses to this adult ADD/ADHD screening quiz, you have replied in a way similar to people who have symptoms of moderate to severe attention deficit disorder. People who have answered similarly to you typically qualify for a diagnosis of ADHD or ADD, and have sought professional treatment for this mental health concern.

If you were diagnosed with ADHD, it would likely be of the Combined presentation, as you indicated significant symptoms of inattention and hyperactivity/impulsivity.

You indicated that several of the symptoms were present before age 12.
You indicated that the symptoms occur in two or more settings.
For ADD or ADHD to be diagnosed by a mental health professional, usually the symptoms must occur in at least two different settings (like school and home, or work and home), and they must have lasted at least 6 months. Symptoms typically worsen in situations that require sustained attention or mental effort, or that are boring.