I can absolutely sympathise with you. My OH is just the same, he's always been lousy with money, but at least up until last year he admitted it and we were able to mitigate the issue.
His salary was paid into my account and I dealt with all the bills, he got pocket money paid into a savings account for him to access as required. Any time he needed extra money for something he'd ask and I'd find it from somewhere. It's no way for a grown man to live but he was OK with it.
Late last year he decided that we should separate our money and I was thrilled to agree. I'd been wanting to suggest it for a while myself as his spending was spiralling out of control but it was so much better to have it be his idea. I can think of only one reason why he suggested this, he thought he'd have more money to spend if he had control of his own salary, sadly, for him, it hasn't turned out that way.
Now we each have our salary into our own accounts. Direct Debits have been split with mortgage etc on the new joint account and otherwise things which are our own personal responsibilities coming out of our own accounts. On payday we each pay in a set amount for half of the joint expenses.
The first month of this arrangement he was broke a week after payday! I told him I would lend him money to bail him out that month but never again. He spends more than he earns every month, I've basically written off the last of my redundancy money, it's what remains of our joint savings, any time he needs extra money I lend it to him from that. Once that's gone he's going to get a nasty surprise as I refuse point blank to lend him a penny from my own money any more. With any luck that will convince him that divorce is a viable option, if he knows he can't squeeze any more cash out of me.
If I take the kids out, buy them McDonalds, get them gifts then I expect to pay for that myself, no problem. If he does the same he expects to be reimbursed out of some mystical slush fund, although where he thinks this slush fund comes from when he doesn't pay into anything like that I've no idea.
Sorry for turning this into a rant, it's too late for us, I've been enabling his poor financial management for far too long, you need to stick to your guns, he'll learn or you'll leave him, either way will be better in the long term than getting into a pattern where he permanently expects you to 'lend' him money that he will never re-pay.