HEAT PROTECTION TIPS FOR HAIR PLEASE?!

So I'm getting worried for my hair.
I'm a 21 year old Asian with Pakistani ethnic background and my hair is moderately wavy/curly. It's up to the middle of my back and whenever I go out I straighten it because I prefer it straight. If I'm at home I leave it wavy. 
I use heat protection before I straighten my hair and often use mustard oil on my hair too.
I don't like tying my hair, I just like it out and long and straight. 
I feel my hair is falling out now though. 
Any tips?