My 1 month old choked on nothing why ?

Just tonight I was sitting on the couch talking to my partner after he got off from work and the baby was in her little chair with her pacifier all of a sudden her eyes went big and it seemed as if she was choking or she couldn't breath. The first thing I thought was the pacifier had fallen apart so I took the pacifier out of her mouth picked her up and starting patting her back but I was so terrified my partner had to take her. She was like this for about 5-10 seconds (although it felt like an eternity) after she finally caught her breath it seemed as if she had a sore throat and she had to catch her breath every 30 seconds or so. She seems fine now but I would really like to know what this is and what can I do if it happens again because I do have a tendancy to panic. And when I panic I can't do anything. But maybe if I knew what to do I wouldn't be so scared. And also earlier today when she was in her chair when she was awake she jumped as if something had scared her but there were no noises or movements to scare her and she arches her back while lying down alot. I am so scared and I am so afraid to go to sleep and leave her alone I am afraid if someone isn't there something will happen I am still shaking and I really don't want this to happen again. Thanx