Feeling financially betrayed

My fiance has been hiding purchases he makes at the store he works for (I have a store credit card, which he uses). In the last 3 months or so, he's been handling the payments in store. I thought we owed $330 (checked balance in June). I know he's taken money out of the account to make payments ($400 or so). I recently found out that we actually owe $850 and this is after a $200 purchase I asked him to return. I am so upset over this - we have two little kids (I stay home and school them as well), and probably $15K in debt (all under my name - credit cards). The majority of the purchases were for him (clothes), some were for our kids and myself (clothes, shoes on clearance + employee discount). I cook from scratch, a lot of our girls clothes are pre-owned (some of mine too), we do not go out often, I try to keep it as frugal as possible. If we didn't have so much debt, and tightened more (the way I would like to). I am upset over the new debt. I have been selling stuff online to decrease our debt, and this feels like a huge blow. We are both old enough to know better. I don't understand his choices and he doesn't seem to have an answer for me. I am angry over the $, and feel betrayed and disappointed. I feel like I am sacrificing my time (devoting a lot of time to sell), going without my "wants" so our kids don't lack anything, and only digging myself a bigger (financial) hole. How do I come out of this?

He purchased clothes and shoes. The majority was for himself, some for our kids, some for me (mother's day), some for re-selling.