hi there, i have undergone exactly the same problems as you had, i never been able to complete my projects on time and i totally can understand what you mean by "deadline doest make sense".... i too had the same feeling, and because of too much delay in projects, some clients have even cancelled the projects and not paid me a bit. i am self employed by the way, have resigned my previous job 3 years ago because i am unable to perform good in my job. recently things gone worse and when i researched about the issues, i found there was a disorder ADHD and all my symptoms matched the symptoms of ADHD...but i was quite happy that there is a solution .... BUT, i too wasnt bad at studies at all, i have successfully completed my bachelors degree but i am only an average student..
i went to a phychiatrist the very next day, answered a questionare which was long, and after 2 days which is today, they told me that the symptoms match more like Anxiety disorder instead of ADHD and precribed an anxiety drug and told me to try for one month and see the effects .. i was angry and thought the pshychiatrist was not knowlegeable enough, but after googling about ADHD vs Anxiety, i was able to understand that both symptoms are almost same but a few unique symptoms that distinguish both... in short the main difference is "ADHD'ers do things without thinking, Anxiety'ers think too much and dont to anything" AND both have sleeping problems but it is very worse for Anxity'ers ... once i understood i realised that i perfectly fit in Anxiety category and was happy that i am in good hands.. other symptoms like, lack in concentration, unable to complete task etc are common for both disorders. but i OR the phychiatrist are still not sure Anxiety could be the exact issue, i will have to try the prescribed drugs, if it works, its fine, otherwise we will have to take the next step. this will obviously take some time to precisely understand the issue. an Anxiety drug for ADHD is ok, but an ADHD drug for Anxiety will make it more worse, now i see some hope in life...
so, i highly recommend you research on ADHD vs Anxiety and see where you fit in AND MORE IMPORTANTLY go and see a pshyciatrist asap and fix the problem if you think you have the problem, because, even after you start the treatment, it may take several months to feel the difference and also to exactly find the right spot and with which drug you are more comfortable etc, you need more patience on this, once you identify the comfortable zone, life will be more easy!!.
we dont want what the world is thinking, we need to the get the job done and make our life comfortable. even if you dont have any disorders, its good to take a checkup if the problems are affecting the life style. you see, everyone have a disorder of somesort, but most of the time, it wont affect their productivity, so they dont take a checkup, we are no way lesser than others.. just that our disorder is affecting the productivity and its a smart thing to act in the right time!... convince your family in a polite way and make them understand that seeing a phychiatrist is very normal, even many people with depression see phychiatrist, there is nothing to worry in this at all!