I didn't tell many people about my ex's drug addiction, but the few people I did tell, I regretted it. My neighbor and I became pretty close when he left- she was emphatic that she wouldn't take sides, and that she wanted to be of help to me and my two sons. She started prying, and I felt comfortable enough to tell her everything. She seemed to believe me until a few weeks later when my X got in touch with her husband and told a completely different story. Ever since that moment, I haven't been able to tell her a thing- everything is met with, "Well there's two sides to every story." Yes- the truth, and a lie! It drives me crazy- makes me want to bust out my stack of paperwork showing he forged my signature, drained my bank account, the social worker report, everything. But I won't. I'm done trying to make people see who he really is. I tried for years to show his family, and then I tried and failed in mediation. Only time will tell. He'll test positive or do something stupid- something he can't whitewash. And if these people come to me with apologies, I'll accept them graciously and then have nothing to do with them ever again.
That's my story.
As for letting him back into your life, please let him prove himself FIRST. It rarely works the other way. Addicts need to discover an entirely new way of living, and sadly, after a while of enabling them they begin to associate us with using. You need to break that association, and that takes time- and a whole lot of dedication on both of your parts.
Best of luck.