Hi Gem: I'm sorry you had such a tough day. You are right that working full-time with depression is a difficult thing. I'm not sure if you have anxiety to go with it, but that makes it twice as hard too.
I wouldn't take the things said to you at work too personally, especially if it is from co-workers. People at work are not meant to be your friends. Even if they are friendly at one point in time things always change as your work environment changes. Also, many people are just catty or mean to begin with.
Last, when you're depressed it is harder to ignore some things or laugh the stupid things off. Since you feel so awful inside and perhaps physically --everything and everybody around you is so much more difficult to deal with. My advice is to take some time and do something special for yourself tonight. Perhaps a bubble bath, a long walk outside, or curl up in front of your tv with a takeout meal. And go to bed early, because being tired with depression makes everything so much worse.
I hope you have a better day tomorrow. And if you need to vent again or talk please come back. We've all been through this too and are here to help.