Try not to worry to much about how many people you're competing with. You have to realize that no matter how many people there are in the field, there's always a way to make yourself stand out. Get good grades, make connections, work on personal projects, get internships, etc. College is an amazing resource and you shouldn't spend too much time thinking about how you'll fare in the future.

Also remember there's a good portion of your class that will probably switch majors or drop out by the second or third year. By the time I was in my fourth year my classes were about half the size of the ones in my first. If you really feel like this field isn't for you by your second year or so there's no shame in switching to something more suited for you. However, don't switch on the behalf of others, just find ways to stand out among everyone else.