If you suspect dyslexia, there are specific tests, such as the CTOPP, that get at underlying phonological processing skills and when combined with other testing - ability, achievement, memory, etc - can identify reading issues. You'd want to discuss these with a psychologist. We can help you find previous posts if you're having trouble tracking down relevant ones.
Your comment about nausea when reading, however, makes me wonder about visual processing. (Not to say it can't be both. Trust me on that one!) An exam by an optometrist or ophthalmologist who specializes in visual processing (not just physical vision issues) may be helpful too.
