Why does my chi puppy heave and gag when she eats?

I just got a Baby chihuahua, she is only about 7 weeks old. i got her hard puppy food and i put water on it to make it softer. After or during the time she eats, she starts heaving like she is trying to vomit. She never actually vomits, but i can tell when she may have coughed something up because she will cough harder once and then chew a little. anyways i dont know if i should change the food or if that would make it worse. and its not that snorting/hyperventalating thing. please help