Ok so I like this girl but for some reason some days ill like her and other days i wont?

Ok so I like this Girl but for some what reason sometimes i Cant stop thinking about her and then nother day's id rather she just be a friend and I like her alot but then somtimes I think she also thinks of me as a friend and also when i go to sleep i cant beacus im always thinking of her is there something that i can do to help me with this problem ?