I'm going through something very close and I think you have executive function disorder and underlying depression/anxiety expressed, or in this case masked, by alexithymia. The executive function disorder is obvious as being unable to perform tasks which one see's as easy due to an unknown mental block or bad planning is a key stone trait. An underlying case of depression or task anxiety also creates/worsens executive problems.
My main interest is your feeling of inexplainable uncomfortableness before a task and generally being uncomfortable existing as a sign of alexithymia. Alexithymia is a trait were people feel the reactions emotions bring, but they can't interpret them which often leads to them confusing emotional sensations for physical ones. The best example I can think of off the top of my head is from the book emotionally dumb; Paul is driving to a party with his gf. His heart is racing, but he can't tell what it means. Is it because he's anxious to be with his girlfriend? Is he mad he was cut off? Is it because he forgot his heart medication? This ties into you because your uncomfortableness sounds like an alexithymic interpretation of a negative emotion. Instead of having easily identifiable emotions and their causes, I don't feel good because I'm bad at X, you have vague problems and even vaguer emotions you confuse for physical discomfort, when I can't do something I feel tingly. You're obviously not happy right now, so your general depressive mood could be interpreted as your always running discomfort. Most people don't feel good before starting a task, especially people with executive problems, so your discomfort before tasks is an alexymic reaction to emotions.
What I recommend is you buy, preferably pirate, a book on skills to combat ADHD and/or executive function. Along side that you should read a CBT/DBT therapy book on anxiety and/or depression, which ever one you relate to most. Alexithymia is the more niche condition, so it has no books. The best you can do is make an emotion diary were you try to connect your body sensations to an emotion based on the context they appeared, My face feels red + I was just insulted = Angry? Embarrassed?. An emotional wheel could help.
If this doesn't work move to therapy, if you're to poor try online of sliding scale, and if that still doesn't work do drugs, most likely start with ADHD drugs as those are the cheapest.
My experience is that before a tasks I would get a vague emotiPost too long. Click here to view the full text.