Beverley: I reflected overnight on the advise I shared with you here. And this morning I spoke with a fellow priest. She and I often chat about issues on AB.
My primary concern is regarding your statement that your son claims he was 'hurt by his father's girlfriend three weeks ago.' I can't imagine a 2 year old being able to articulate time in such a way. So I guessed you were referring to the last time he was with her.
However, if he has said he was hurt by her, I hope you had him try to either act out, or explain to his ability what happened. If he commented that she hurt him three weeks after the event, but in the instant he saw her, he clearly has sufficient memory to recognise that he is not comfortable with her. And as such, you need to seek advice.
However, in the dynamic of failed relationships, especially when there may be the pain of seeing an 'ex' moving on, it's important to ensure nothing is being seen in your eyes that isn't there.
I wish you every success
Fr Bill