Lately I’ve been having trouble writing the number three legibly. It’s called Disgraphia and it’s not a good thing

Speaking as one currently involved in all things Neurological and skeletal, i agree.
If you're worried you need to mention it to your Doctor ASAP.

Of course there are also possibly a dozen other explanations nowhere near as terrifying as your imagination is creating. You should be aware of that too.

Turn the page sideways and write a m

You know , speaking as a left hander, I've always thought that threes must be hard to write for right handers ....it just seems harder than the other way round.