I Need Advice

So I have recently moved schools about 3 weeks ago, once a week every Wed we go to this other school for PE/heath and 2 options (Since we don't have enough classes yet at our school) Anyways so I found out that my mum and my PE teacher use to be "friends" While my parents were taking a break, they got drunk together, but my mum didn't say anything else happened. On my first lesson with my PE teacher after he found out I'm her daughter kept on looking at me non stop, the week after that I was sick on Wed so I didn't have him, but this week, he did the same thing, he would keep looking at me, my friend saw it too, she said he was looking at my butt (but I don't know if she was lying or not) I tried my best to avoid him the whole lesson, when everyone left to go change out of PE gear, I had to ask him if I had to to the assessment, He said no don't worry, then he touched the front of my shoulder for a good old 5 seconds. It would have been a bit more normal if I had known him for a month or 2 but not after my 2nd lesson! Is that weird behavior? I didn't tell my mum about it. What should I do?