Having major problems with processing written information. What can I do?

Hi. I (18) have been having problems with processing written information for quite some time now (4 – 5 years) and it is really starting to stress me out.

I noticed that this decline started happening when I started to develop really bad mental health issues and anxiety, but I am much better these days. However, it seems as if the problem is just getting worse.

Things I have noticed are:

1) I tend to process the words better if I highlight every damn word or if the words are on coloured paper (as opposed to white).

2) I need to re read sentences over and over to understand them a lot of the time (especially in paragraphs and essays) and it really stresses me out. Sometimes I do it to the point of having a headache.

3) I wear glasses and at first I thought that perhaps the prescription was wrong. However, I changed it a few months ago and I am no longer having headaches. The problem is that I am still having these processing issues.

4) I am suspected to have autism and I am waiting for an assessment. Has that got anything to do with it?

5) I was THAT kid that read like 10 books in 3 days and now I cannot read a single book without getting bored or not retaining the information. It really sucks and it feels like it has stunted my vocab a little.

6) If the text that I have to read is boring, then the chances of me getting through it without re reading sentences, getting distracted by thoughts/future events or things becoming blurry are very low.

7) I cannot skim. Tbh I always found it difficult to skim read but now I gotta read out loud and I've got to read in a very jaggered manner so that I can process what I am reading.

I really don't know what to do. I am worried because I already dropped out of sixth form some months ago because of my bad mental health and now I have a fresh start. However, I am so stressed about the first essay that is due because I keep re reading and not processing my own goddamn words. Anyone know what I can do?