My wife is a thief!

Recently it has been brought to my attention that my wife of 17 years is a Theif! She has stolen money from my family and prescription pills to sell from my family! I confronted her, but she just stays in denial, even though I know it's true! She just says I'm accusing her to try to end our rocky marriage! But the facts are all there and I've suspected her of stealing for quite awhile, but never confirmed my suspicions until this past weekend! First my brother asked about money he was missing, then my mother confronted me about some pills and money she was missing this last weekend, and we were the only ones there! What the fuck do I do? We have kids and she's currently pregnant again! I can't hardly stand to look at her knowing what I know! And she just denied it ever happened. And it's not the only time or place or person! Help I'm so lost and alone!