Guilt Over Not Speaking Up Earlier

AITA for not speaking up earlier? Context: A few months ago, I broke up with

my ex-partner. For the last few months, we were in a polyamorous relationship with

another person. That person and I stayed together after both breaking up with our ex-partner.

I will refer to them as my girlfriend to avoid confusion. I am unsure whether I should feel guilty

about how things went down. The relationship itself was actually good for the most

part. Some things that should have raised concerns already happened early on

though, for example, my ex-partner messaging a friend of mine pretty mean things

because the friend was a smoker. But we were both young at the time, so I thought it