Is it cheating if your Separated?

I had been with my ex for 10 years this month I'm 30 he's 29, we got married in 2014 seems like It all went down hill from there. We have been separated since October 2020 his Coke/crack addiction was just outta hand and he told me he didn't want to get sober or go to rehab. I met someone also separated from their spouse. Is it cheating like both our ex's seem to think. Cause I thought we both were clear in the fact it was never gonna work. Also to add I'm pregnant with my 5th slim chance it's my ex husband's but always that slight chance I fell pregnant in October of 2020 after meeting my new guy.