Hi, Jennifer

First you need a ((((HUG)))) and then someone to tell you that it's going to be okay!! And you know why???? Because in reading your post I can see that you really want it to be okay. And it will be because you are fighting for it to be.
Nobody here is an expert but I have done alot of research trying to help my daughter who has just recently been diagnosed Bipolar. For one it your mom is Bipolar there is a good chance of you having it as well. And it IS treatable so that is the good news. Also, it is a known fact that Bipolar will be triggered or worsten during adolescence when hormonal levels surge, after the birth of a baby (postpartum), or during menopause. So you fit the criteria there as well.
You definitely need to go to your doctor and get the referral. I really am impressed with the fact that you want to get help, most people will avoid doing so but you will get better because you want to. The first step to getting there is getting to the doctor. From there it is trying to find the right treatment and meds.
Do you have any extended family to call upon for support??? I know that this must be a difficult time but it is soooo important for you to take care of yourself. You need to get enough sleep, eat right, and exercise.....that is so important not only for a new mom but especially for somebody who may be Bipolar. Any stress you can alleviate is sooo important so do not hesitate to call upon friends and family to help you out when hubby is unable to.
We are here if you need to talk to someone.....venting is another good thing to do and will take some of the pressure off of hubby too.
You will be alright.....you know you need help and I know that you will get it. Make that appointment ASAP....the sooner you get to the doctor the sooner you will be on your way to feeling better.
God bless you for being such a wonderful mom to your kids....they are lucky to have you. ~ Goody