I'm a tutor and have taught some students with ADHD. It is a really horrible thing to have to deal with, especially when severe.
So - my advice.
Go and see your GP. Explain what you've said here and take a list of the symptoms that are most prevalent/bothering for you. Make sure he/she knows how it is currently affecting you at work. Ask to be referred to a specialist who can formally diagnose whether you have ADHD or not and will be able to advise you on treatment options.
As I understand it, there are non-drug treatments along the lines of counselling where you are helped to find strategies to keep you on track and deal with the worst symptoms. There are also drug therapies. The drugs can have serious side effects but I have seem them make a really dramatic difference for the better too!
Once you have seen your GP and he/she has referred you, I'd talk to Occupational Health at work explaining that you have been referred to see if you have ADHD and ask for their suggestions/advice/support.
I hope you can work this through to the point where you are getting some help for the issues.
In DIY - help yourself terms.
Be rigorous about getting decent sleep if you possibly can. Ban yourself from anything involving electronic screens after 9.00pm (8.00pm if you can bear it) as the light from screens interferes with melatonin levels in the brain and you get less restorative sleep (REM sleep). People with ADHD often find it harder to sleep and are might be more adversely affected by things like light levels. For the same reason make your bedroom as dark as you can at night. Give time for these things to have an effect!
You could try taking fish oil supplements with a high level of EPA Omega 3 in them. Some studies have indicated that these have helped children with ADHD type symptoms but the science is debated.
You could experiment with how you function after a strong cup of coffee. Some people with ADHD find that they are better able to focus with some caffeine inside them (I'm not advocating routinely self- medicating wit h caffeine though - if you are willing to take drugs to help then you are better discussing options with a trained Health Care Professional)
Try writing "plans of action" for any longer or more complicated tasks you have to do. Get in the habit of repeatedly asking yourself "Am I still following my plan?" and checking back with your plan. Hopefully this will help to keep you more on target with things!