Hair falling out in clumps?

I always shed hair a lot, I have very thick curly hair and when after having a shower or whilst straightening it, a few strands used to fall out. However, in the past fortnight I have begun to lose clumps of my hair. I lose a crazy amount of hair in the shower, and when I straighten ir/tie it up/brush it etc clumps of it come out. I'm studying for final exams and I miss my boyfriend a lot, as he lives in America and I live in Europe. Could stress be the cause of it? Should I be worried? And how can I prevent this hair loss? Please help!