New here. New situation

So my ex fiancee jumped into a relationship pretty fast after our BU - within 3 months.

Since then, she moved in with him 1 month later and has since moved our 3 year old daughter in too. All within the space of 2 months of being with him.

Now, 3 months in total of their relationship I am finding out that he is having our daughter at times alone - someone I barely know and my ex barely knows.

I have asked what happens when my daughter needs the toilet. She said he helps her. I raised my concern and said I am not comfortable with this kind of situation. You both barely know this man. I was met with a message of disgust and accused of being immature.

Am I wrong to feel that this is a big deal? For me, it isn't right. Am I being too over concerning?