Please help! a bit embarrising.?

Okay I'm 16 years old now and ever since I can remember English hasn't been my best subject I don't know if I have been diagnosed with dyslexia or somthing but my grammer has always been horible I don't know when to put comas and periods and I really find this emberasing when I have to type or work in groups at school I also have problems with when I start a new paragraph when I was in the second grade I repeated for reading slow when I was in 7 grade I took and a reading test twice and I got a score of a college reading level how can this be? My spelling is horrible my reading out loud is worse but when I read by my self at my own pace I do great in texas we have a test called taks that we take each year to determin weather we pass or not well on the english one I have always gotten recomended how is this possible?