In answer to your question "should i trust her?"
probably not...
I would suggest educating yourself on addiction ....start by reading posts and stickys at the top and keep posting....
you will need to be aware of your finances and secure all money and valuables asap
also you need to be sure that the children are not in harm's way
it sounds like she used during the pregnancy...how is the baby??
september is not that long ago....i doubt she is a "new" person in october
she probably does want things to be different but it is not that easy...addiction is a horrific disease and it sounds like she needs help and a strong desire to change
please take care of yourself and the children
alanon or naranon meetings would be so helpful
it is a difficult path....
I will keep you in my prayers