Was I the other woman?

When I met my now ex boyfriend he was still living with the mother of his son, he told me that they were separated for more than two years but lived together for financial and parenting reasons. When he decided he wanted to date me he was honest about this and reassured me that he was telling me the truth, he asked me to wait a month for him to move out as he needed to get his finances in order first. I agreed to be his girlfriend and we dated for a month. In that month we saw each other daily and talked on the phone every night until three or four in the morning, he always answered my calls. Truly, he never gave me any reasons to doubt him. For events unrelated to this issue we ended up breaking up before our first month together but remained friendly, he got his own place just like he promised and moved out after I broke up with him. I know the situation was sketchy to begin with and I probably shouldn’t have taken such a risk on the first place but I think I was lucky and he didn’t lie to me. Do you think I was the other woman?
Was I the other woman?
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