I'm still pretty emotional at 2 months PP too. It can range from sad to happy to pissed off, but I'm usually pretty mellow so all this up-and-down stuff is driving me (and my husband!) nuts. But its usually related to sleep- if I don't sleep enough, I'm a wreck, and if I'm somewhat rested then I am a lot more stable, LOL!
I had PPD with the last baby and the difference was that I felt either angry or totally overwhelmed every day, ALL the time, and this time I have a lot of joy with my little girl (and my boys!). The overwhelmed feelings come in moments, not days or weeks, which I think is normal.
Plus, you are dealing with an outside circumstance (i.e. your husband leaving) which is a BIG deal when you just had a baby! Don't be too hard on yourself, but if you start feeling sad and down all the time, then it might not hurt to get help. Sounds normal to me though, I'd be a wreck if my DH left right now.