Trying to focus on AS but my boyfriend is getting in the way ... what do i do?

AS/Alevel exams are VERY important for determining your future hence why i said to myself i will not have a boyfriend this year. However, i do now, he is amazing but i feel like i am letting myself down as i am distracted and less focus than i use to be - its not his fault, its mine ... how do i overcome this distraction so i can just focus on my work?