Is it normal that i can't give blowjobs?

You can do a fairly good job by just playing with the tip; like the first 2 inches kinda thing. That way, it doesn't hit the back of your throat and it does feel really good. Most of the sensation is in the tip anyway.

Hey, first your bf needs to show some respect and stop forcing his cock his cock where it doesn't belong. My girlfriend has been giving head for the last twenty years without gagging on cocks pressed to deep in her throat. When she sucks my cock she puts only the first two or three inches in her mouth and strokes the rest with her hand at the same time.
Hey, seriously, you don't owe your boyfriend blow jobs. They're only yours to give how and when you want. If he disagree he blow himself.

The only thing you can do is practise. The more you do it the less you will gag. Another thing most men like it when girls gag. Or just dont deep throat!

It's normal at first but worth the practice to learn, lots more info on Internet about techniques, but here is not the place

the names wrong you dont blow

You get used to it. 3 years for me and I still get a bit of a head-lurch (no actual gag though), but HUGE improvement from my first time.
Don't go deep, make sure you are in control of taking him in (don't let him lean into you), and take it slow. You will build up a tolerance.