When you're feeling more calm, and have a clear mind, you should jot some notes down: what you expected the job would be like, and then write how it's actually going. What is going well, what is not etc. (pros cons)

I would be prepared to accept what is given to you, and own it. Apologize. Then, tell the supervisor that you are grateful for your position in the company, but you have some concerns... use the points on the list as your reminders of what to focus on.

I feel you--I have cried at work. I'm in hospital nursing leadership. I've had many nurses crying in my office, that I have had to be the rock for...and luckily I have been able to cry in my bosses a few times as well.

Find a person you can vent to about work too. That helps so much!