Hi i can relate to your story i found out my partner has been using cocaine since we met, i had no idea. He had been going out to his van on our drive doing it then coming back in the house. But looking back with the information i know now the signs were there.
I completely understand what you mean about the lies, the lies have tore our relationship apart more than the drug use. He too suffers with depression and used the drugs to escape that. He used to spend days in bed, he was snappy, paranoid, just not a nice person to he around. He is on antidepressants now, and was seeing a drug counsellor but only went 3 times and then he made excuses not to go. He says hes been clean since xmas but i cant 100% believe him with all the lies hes told in the past especially regarding money. Hes so sneaky.
He has made some improvements, but because of everything i have just lost all respect, theres no trust and i feel angry towards him for spoiling what we had. I can completely understand where you are coming from. Its made me check his wallet and his pockets, seeing if theres anything to find. Im a trusting person but hes changed everything.