First of all, can I say that having 4 kids and another on the way, you deserve a medal lady!
I Googled your condition and saw there are a couple of treatments for it like Femanax, Vagiclear and Balance Activ - have you tried any of these before? Being pregnant, you will need to clear using anything with your OBGYN and you might need to wait until baby #5 is here safe and well to start trying these things.
I did have a friend years ago with a problem like this and she was told to (please don't read this is you are queasy!) get a tampon and dip it in natural yogurt and well you know, ummm put it where a tampon usually goes, ahem.
It did work for her as it re-established the right kind of bacteria there.
But speak to your doctor before trying anything and good luck.