Single mama...?

Jaci • Baby #1 EDD Oct 16/15!!
So long story short, married my husband last summer. Together for 2 years before that. Had some ups and downs along the way. He was in NA when I met him as he had a previous problem with prescription pills.
 He "relapsed" 1 time before we got married. Since we have been married, he had admitted to using on 2 more occasions (for weeks/months) And buying more then just pills. I have gone with him to meetings and tried to keep us going. 
Ontop of those issues, I am 3 months pregnant. Money keeps going missing from our bank, and he's getting home "late" from work. I know he's lying to me, and am about 95% sure he is using again. I have set up a marriage counsellor in the next few days, but honestly... I do not think I can do this anymore... Especially with a child coming into my life. 
I don't know what to do ...