Problem paying attention. To consult?

I try hard everyday, sometimes harder than my friends but I still fail at what's considered normal. When I try to study, I lose focus so easily that I end up reading the same line over and over again and sometimes spend an hour reading the same page. When I read, I miss small words and sometimes read 'isn't' as 'is' and miss out 'not' that changes the meaning of the sentence. I am 21 and I still get confused with spellings that have more than one vowel (spelling separate as seperate or separete). I also day dream to an extent where I want to enact my dreams, and I get so lost in them that I sometimes believe that's the reality. I thought all this was normal until my friends pointed out that it isn't. I don't know if I'm just really stupid and not trying hard enough or if I have a learning disability, and I'm not sure whom to consult regarding this. Please help!