Work related stress. What should I do?

I have been working for my current employer for many years. I used to like what I do, but recently I really hate my job. Every time I step foot inside my work area I start feeling stressed and the only thing I think of is just wanting to go home. I think I am stressed because their are many around me who do not do their job correctly and many times, everything falls on me. I went on vacation a few weeks ago and the day before I had to return to work, I had a panic attack. Yesterday a customer yelled at me for no reason, and I ran to the bathroom to cry. I didn't even do something wrong, I just asked him if he needed help and he snapped at me. Obviously anyone who reads this thinks, well just quit and find another job, but I have a big problem. My husband has been laid of for 4 months, so right know I am the breadwinner in the house, and I just can't up and leave my job because of the financial responsibilities I have. I have a Bachelor's in Biology and I have tried to find work in that field which would be less stressful, but I haven't been very successful. I mean, I spent 4 years in college and I feel that I should start using my Bachelor's for something. I am very good at what I do right know, and I am always ahead of my game, but I am not happy their anymore. My managers are always happy with everything I do, but I feel that I always have to find another way to impress them, and I am never satisfied with just being me. I don't even call out when I am sick because I feel everyone depends on me. Any ideas?