Some medical universities let you do their course with just biology (a certain small amount though so you'll be restricted). If you don't want to do chemistry, look how heavy chemistry intensive medicine is because it might not be the course for you. Look at what courses you like and see - it's always safe having two science subjects though, which psychology counts as for most unis, for courses you will like. My friend thought she wanted to do medicine but turns out she didn't like it so she wants to do clinical psychology, which you might like.