I know it's hard. I have gone through the same thing. I'm 21 and have always had issues in medium to large crowds, but until I lost my driver's license, I was able to keep it in check.
I started depending on other people to get around. I got pregnant with my first child and my husband went to every appointment with me, we went grocery shopping together, I rarely left the house without him, and never by myself. And since he's always been a third shifter, most of my days were spent in my home. For about two years, I didn't get out very much and, like I said, never by myself.
Even after I got my driver's license back, and my husband wanted me to do the grocery shopping without him and run the errands and stuff, I had a lot of trouble doing it. When I was in high school, I was diagnosed with a panic disorder and severe depression, and all of that came whooshing back down on me.
But, I learned to cope. If you aren't too keen on getting professional help, like I'm not (I've had some bad experiences with "professionals") then I just suggest taking babysteps. Start just by going out the front door alone. Each day, take more and more steps away from the house. After awhile, take your husband to the store with you, but leave him in the car. Eventually, you'll be able to go out and about like you'd never had a problem.
That's how I did it, and now I take my two kids grocery shopping with me and have no problem, though I do still (and always will) avoid large crowds.
If you aren't averse to professional help, and can do so, I really suggest you talk to someone. It's a lot harder doing it without the support you can receive from a professional.
Maria