It would be a good idea to get a second opinion and possibly stop taking the Zoloft. I was initially put on Paxil for Depression. My mania was missed in the diagnosis because I'm bipolar II, which means I only have hypomania, which often goes unnoticed. The Paxil exacerbated my bipolar and I went from having episodes lasting for weeks - months to having episodes that lasted for mere days, sometimes hours.
My advice to you is to keep track of your moods. You can do this very easily by making a number system. 1 being suicidally depressed, 5 normal, 10 very manic. You can add your own behaviors depending on what you personally exhibit. Keep in mind that mixed states can occur too, where you can feel very depressed but be agitated, cocky and take risky behaviors. If you make a scale of numbers, then keeping track becomes very easy.
Take this to your doctor (and possibly a second doctor) and let them know what behaviors you're experiencing.
Because of the hormonal changes taking place in our bodies during pregnancy and childbirth, preexisting tendencies towards mood disorders are heightened even further.
Be safe and don't wait to get properly treated. My 2 cents. Take care of yourself and let those around you care for you too. Whatever you do, don't beat yourself up. We've all been there and I know it's scary. Build a network of supportive people around you and do whatever you can to nurture you. Bring your family to counseling with you so they can understand and be aware of your symptoms and be a support to you.
I hope you are able to get some answers soon and start to feel better. 
