I have not had severe bouts of panic attacks, but I have had them.
From what you posted, I would say anxiety sets off your panic buttons. This time, it happened to be that you didnt know where you BF was....which made you anxious, so that set off your panic buttons.
I would suggest getting a punching bag or punching clown. Next time you start feeling anxious, dont let it become a panic attack, get into punching the bag or clown.
You need an outlet for this anxiety before it puts you into panic mode. I would suggest physical exercise of some sort, hence the punching bag or clown. You can also try going outside and skipping rope, playing ball, riding a bike, or jogging.
The physical stress you get from anxiousness gets released during physical activity. Thats why you cut yourself or put your fist through the window.....that stress has to go somewhere. Just dont let it come back on you.
You have to find some outlet for your anxieties so they DONT come back at you and you end up harming yourself. Im sure that freaks out your boyfriend, and we dont want him having to worry about you.
I would also suggest that if he is going to be gone for more than 30 minutes to an hour (other than work), that he should call you or leave you a message, so you DONT get anxious and then go into panic mode. Do you guys not have cell phones?
Find something to work out the stress when you feel it coming on, and you will feel better, instead of harming yourself.