1999 Mercedes Benz C230 My Mercedes wont let me in!

I was at the gas station the other day and when I got back into my car the alarm went off. So I got it to stop, not sure how. I went to work and when I was done with my shift my car wouldnt let me in. I tried to use the key, but it still wouldnet let me in. I eventually held down the unlock button and it rolled all of the windows down. SO THat is how I have been getting into my car. Untill today, I need gas. And as ironic as this situation is, the car wont let me into the gas tank. I need help!