Why is it that I've only had a panic attack once? Could I have had other times to?

I think you should reflect on what caused the panic attack. Maybe it was a big thing and you were really nervous. After you learned how to manage certain situations and know there is nothing to be scared of, sometimes the fear goes away. Maybe you had one and didnt notice? What made you know you had a panic attack? Reflecting on the Situation and what you felt in the Moment can make you realise and see thing you might have missed before! But I really hope things will get better for you in the future. Remember that you are not alone and can always reach out to someone.

you might have had panic attacks without knowing thinking its something else, when you feel stuff out of nowhere try to think of why. there are a lot of different types of panic attacks and yours may vary depending on the topic of why your having a panic attack, sometimes there wont even be a reason and even if you havent had any at other times its good you dont have to worry about having only one, its normal for some people to never have panic attacks and burst out and have one huge panic attack. i hope you find a solution