I'm doing 5, but as you can see in my sig they are all humanities, so therefore are not nearly as hard as the sciences.
Doing all the hard sciences and then some humanities on top is bad idea, and you probably won't be able to do it anyway. At my school people who are taking sciences are finding them their toughest subjects.
Pick your direction, and take 4 would be my idea. We can't all be polymaths unfortunately. There are not enough hours in the day...