do you have long hair? the natural loss of hair is more noticable when its long. Mine sometimes looks like im losing loads.
If you find no spots of baldness then im sure its just normal loss
If so then this is the most likely reason. I used to use my straigteners every day and had the same problem as you. I now only do it if I really need to and I have noticed a huge improvment. Other things to take into consideration are if your hair os colored as this will also weaken the hair and cause it to break off.
It all depends on how much is coming out really???