Why do my eyes spasm when I try to read?

Hello, I have always had good memory. Lately though, when I try to read and focus on something, its so easy to get distracted, also my eyes seem to jump back and forth between the words in the sentence, even if I concentrate really hard. One more thing, lately, I have been forgetting simple things like doing math with fractions, such as adding and subtracting them, and algebra as well. I practice these things quite frequently and even plan on applying to medical school after my pre med courses, can someone tell me what could possibly be wrong here? Ive been out of High School for only about three years. Thank you