So:
You were happy with your relationship - but he had a gambling hobby / habit without you knowing?
He knows about your money, your inheritance, but is cagey and keeps his own financial affairs close to his chest - even though he has relied on YOU to clear his overdraft?
He 'isn't happy with the relationship' and is thinking of leaving?
He doesn't agree with your policy of not smoking weed now you have a baby - and to appease him in his unhappiness you have let that go.
..oh, sorry, Lucy...I have now read your post of this morning. I'm sorry - I know it must be very very painful to be rejected like that, and very painful to find out so much when you thought you were so happy.
You won't feel it now, but in all honesty, given the little list I posted above, he isn't going to be a reliable, trustworthy, loving partner to you, or dad to your baby.
Your friends and family will hopefully rally, you will get lots of support on MN, and one day, a long way in the future, you will look at what was REALLY going on and be glad he went now, before wreaking havoc in your life and finances. None of this is your fault, YOU haven't made him unhappy, you weren't unreasonable about the no-smoking policy, you can't makle him either love you or behave responsibly by giving him your money - and he has betrayed you and kept the truth from you.
So sorry. But it is true - you deserve better. You sound very sweet and genberous and sensitive. You need someone who respects the role of truth and trust in a partnership.