I have HSV type 2. I had yesterday, and today I'm showing signs of an outbreak. Was I shedding last night?

It's possible that you were, but you would never know as shedding doesn't have symptoms. Shedding usually happens just before and a few days after a break out occurs. If you were taking antiviral medication regularly then that should help reduce your risk of your partner getting it. All you can do is wait and see. If they do get a break out encourage them to get tested. If they don't know of your status you should tell them.