It's perfectly normal to loose around100 hairs per day, but perhaps it looks more because your hair is long, or maybe it's breaking.
Hair should be combed from the ends upwards, so as to avoid breaking the hair shafts. Hair straighteners will cause hair to become dry and brittle, so it may break off at ends and middle of shafts, this would mean you are losing more hair.
You should probably only worry if the hairs are all coming out at the root and if you have bald or thinning patches, but if you are worried, you should see your GP or a Trichologist.