You cannot rely on your partner in any shape or form, as eventually your whole world will come crashing down.
I see Cocaine adicction around me, from all walks of life.
The higher you are the harder and lower you fall.
If you were in Social Housing, in a min wage paid job, you could give him time limits, as you would have a safety net.
If your DP gets found out, he will be instantly dismissed, you won't be able to tap into benefits and you won't get re-housed easily.
Go to your family now, because one day you will have to, but I doubt their reaction will be as supportive later, as it will be now.
An addict, is an addict, the only that changes is how much you have to lose. You, your baby and your DP have a lot to lose, which means he is in deep, otherwise it would end.