Hey mustang,
Emotional rollercoaster is all part of the deal!

Given your history of depression, there is also antenatal depression which is before the bubs arrives as well as postnatal, which i'm sure you already know about.
Just keep a tab on your emotions and seek help if you get worse (i hope not).
But crying one minute, laughing the next, biting someones head off the next minute is all the fun of pregnancy.

Take care. xxooxx