Am I going mad?

I am getting over my ex (and about to start therapy.. this week..phew) but sometimes I get thoughts about him and the way he was and think, was I imagining it/too paranoid? Perhaps he couldn't be capable of what I thought?

One thing that stuck with me. My ex was a teacher, of 16-17 yr olds (he's not now, lost his job). He once said to me and a friend that he said to another teacher that young girls shouldn't wear short skirts in the front row of the class as he may find it difficult not to look, if they had their legs open. Thing is, he said it as if it was their fault for not being dressed appropriately, I think he even went to the point of telling them not to wear certain skirts. And when he was around my 8 year old niece, he used to be all over her, really sickly, "darling this, darling that" and cuddling her. But my sister-in-law, her mother, thought he was great with kids.

I don't know, I think he was creepy, and I used to get scared when I thought of having a child to him. Am I imagining things here?

I know I need to stop obsessing but sometimes I find it hard to work out what was real and what wasn't.