I think it's relatively normal .....
I worry about PPD every time I'm PG, since I've been treated for depression in the past. (of course, I divorced my XH, the reason behind my depression)
To me, mood swings are part of the game .... affected by hormonal shifts, LACK OF SLEEP, increased workload (trying to adjust to changing roles, etc), no time for yourself, etc.
The majority of the time ... I'm pretty happy. There are days when I feel like I have not moved from the couch, and I'm just one huge boob. Other days, I feel like superwoman, for handling all 4 children relatively well!! And, on other days, I want to put on earplugs, and walk down the street, leaving DH with all of them. (of course, I'd only leave for 5 minutes)
I'm short tempered some days, and there have been a few times I've cried, and thought, "I CAN'T do this!" Thankfully .... a few minutes to myself makes things a lot more tolerable.
What kind of things are you feeling/experiencing/concerned about?