I was conflicted with the same thing when my ex and I split. I wasn't sure if I should be honest or just keep it light. Most people that knew us already knew there were lots of problems. I asked my therapist how she thought I should tell others and she told me I shouldn't worry about what others think and what they say about me is none of my business. She said I should tell them what makes me feel better. The truth made me feel best so I told those close to me that he has a drug problem that he doesn't want to fix and therefore it provides an unhealthy environment for the kids and I. I kept it light with aquaintences. If down the road you get back together with him who cares what others think. Trust me, EVERYONE has their own set of problems and its YOUR LIFE and your decision.