I dumped my boyfriend but he thinks this is a stupid reason and that I'm seeing someone else?

we are both 18 and I was dating my now ex for a year and I still really love him, how ever we are both in 6th form and I really want to go to medical school, got our results for our first AS level results andi I got 4 As, my boyfriend got 2As and 2 A*s. (he wants to go to medical school too). Now the pressure is really on for my, I have been working and revising my *** off for my exams and I already got excepted for London Empiral College to study medicine there, so has my ex. All we need to do is get the grades, atleast 2As and an A*. I am stressing about this so much, our exams are 2 months away. So I decided that me and my ex go on a break because i wanted to be fully concentrated on my studies right now to get those grades and wants exam period is over, we get take things from there after all, we are going to college/ university together and in the meantime we can be friends. He however thinks this is a silly reason to break up and the that I have really found someone else, he hasn't spoken to me in 2 days! I can't afford to do this right now! I see him in my 6th form all the time and he blanks me! Urgh! What should I do???? I do still love him and want to be with him but I feel like I cant afford any distractions right now, how can I make him understand that???