Could it be that I'm asexual?

I think it's possible that you are asexual, because it is unusual for heter or homosexuals at your age to feel indifferent about sex. However, I also think that you may be more mature than your surroundings and recognize that uni is not for random sexual exchange. You may be hetero or homo but haven't had the reason to pursue either one. My advice is that you focus on your studies and try to avoid labeling yourself just yet. I'm afraid that if you pick a lable now you'll miss out on something later when it doesn't fit within the confines of your self-diagnosed orientation. You'll have plenty of time once your career starts to pick a category, and then you'll be independent enough to embrase it! Walk with wisdom; live in peace.