Thanks for the replies! =)
I only went for chemical straightening twice, and only air dry my hair. So, not much exposure to heat, unless you consider the sun.
Sadly, I cannot go with braid outs or twistouts even though I think they're cool. My mother will kill me and its not common here at all. Everyone seems to have straight or hair curled at the ends.
Or could it be the sulphate in the shampoo I use? Off to do an ACV rinse now!