How can I improve my reading comprehension?

I could only suggest reading something that you are really interested in. A subject that grips your imagination and holds on tight! Whatever that is as long as you are so invested in it you just can’t put it down.

I know if I’m reading something that is boring I drift off so fast….

One approach that I have seen is to write down some notes about what you are reading. Start by reading the first paragraph and, based on that, write down a summary of what you expect to be covered. Write down some questions that you expect to be answered. Now start reading and write down answers to the questions.

Make sure you are not distracted while you are reading. Set yourself a time to read and turn off your computer, do not jump up every 10 minutes to check Fluther or something else. Think about what you are reading while you are reading it.

There’s so many things that can cause this: Dyslexia, Being Hyper, ADD, Being Bored, PTSD, head injury, Unnamed mental issues with memory or comprehension, etc.
It could be chemical in your brain, or it could be psychological.
I suggest reading the childrens books that feature the character “Encyclopedia Brown”.
These are short 2-page mysteries. You need to exercise the part of your brain that deals with this. And if you are ever bored with the subject matter you’re reading, that only makes things worse.