This is one of the things I have battled with for years. I pretty much have all the theory of reading in my head. In fact I can transcribe a bass line from the sheet music, but you'd better give me an hour (or more). But Sight reading?! Hang it up. I just can't seem to make myself practice reading.
I guess thats the curse of learning to play by ear first and then 10,20 even 30 years later trying to learn to read feels like starting over again.
It's wierd too, I can read tab, chord charts and number charts. But sheet music just seems to give me a fit.
It doesn't get any easier with age either, combine that with all the brain cells I killed back in the 70's, BUT I keep on trying.