Advice?

I just left my ex for the millionth time. I met him when I was in the young, have fun phase. Our relationship has been filled on lies on his part. I wasn't perfect I made mistakes but bottomline I changed and grew up and he didn't. I knew going into the relationship that he did drugs, but thought nothing of it cause I was only bout sixteen. He would usually smoke weed, but he was an addict to spice/k2/synthetic (fake) marijuana. He got off of it. But this year he got into heroin and meth. Selling and using. He's hid he was using for months, till he couldn't deny it anymore. He tells me he's not using or selling even when people tell me he's been hitting them up. The evidence is right there and he still continued to lie. And I still would take him back and take him back. But after today finding out that he's still selling and using I'm done. I blocked him from messaging me, and deleted him on social media. Advice on how to be strong and move on when he trys calling or contacting me in other ways would be great. Because thats usually where i screw up and give him another chance. Also, others stories help.