I can help you with the handwriting and the hurting hand...
Use a fountain pen. Since you aren't used to them, get one with a very solid nib to start with. The point is, first, that your hand is hurting because you have to use pressure to write. With a decent fountain pen (one with decent ink flow) you don't need to do more than touch the nib to the page, then draw it across the paper. You will need time to get used to this, and you might ruin a nib or two at first. But your hand will thank you.
And everyone who uses a fountain pen finds it improves their handwriting, at least somewhat. It won't give you perfect handwriting, but it will improve it. (If messiness is an issue, you also want to give some thought to the inks you use; fast drying and no or low feathering are qualities you want. Noodlers X-Feather is the first ink that comes to mind - but for that you either need a pen that fills from a bottle, or a cartridge converter for your pen.)
I started using fountain pens when I was young - because my hand hurt whenever I wrote. I have always had terrible handwriting - but I got fewer complaints when I used a fountain pen. For a while, I had to give them up (the work I did had me spending time in archives - where any sort of ink pen was forbidden) and have never been so relieved as when I went back to them. Note that I did say "fewer" complaints. You may also need to work on your handwriting - but it will be easier if you're using a fountain pen, and you should get an instant improvement. (The nib of a "real"
pen gives your writing more character, so instead of looking messy it looks a bit more impressive. I don't know how to fully describe this effect.)
If you need to know more about the wonderful world of fountain pens, feel free to post your questions here. I have over a hundred, some expensive and vintage ones, and some very inexpensive. I'm a writer, so writing tools are a huge issue for me. And I've found fountain pen use to be a real sensory pleasure, too.
(If you use bottled ink and not cartridges, it is also - long term - the least expensive way to write, as long as you can resist the costly beauties.
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AQ Test = 44 Aspie Quiz = 169 Aspie 33 NT EQ / SQ-R = Extreme Systematising
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Not all those who wander are lost.
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In the country of the blind, the one eyed man - would be diagnosed with a psychological disorder