Boy it is hard to say.
Could be withdrawal from the Paxil. Kind of a fast taper.
Could be the Paxil was working well and now that you don't have it depression is returning.
Could be negative hypo mania triggered by the Prozac.
Not really enough time yet for the Prozac to work if it is going to.

Maybe try adding some Paxil back while taking the prozac to see if you need a slower taper. maybe the doc thinks that since you are replacing one SSRI for another you wouldn't get any withdrawal but then you said you were fine for awhile so I dunno.

I do sometimes have what I call mixed episodes where I get very irritable and annoyed. Pretty rare for me. Getting totally overwhelmed by things is very common for me. Last night I kept waking up and freaking out about a door replacement job I have to do Wednesday. One day I feel 100% confident about it and the next totally afraid I can't do it. It is not rational because I have a ton of experience to be able to handle the job even though it is a rather difficult one being a commercial metal door in concrete and I am a plumber. But still I know I can do it. It is the irrational depression that affects my thinking.