Shower infront of mother?

im 16 y/o male. normal upbringing, and i some how managed to catch head lice from my stupid little brother who got it from school. ANYWAY the other day my mother put the head lice stuff in my hair while i was playing xbox then when i went to have a shower she came in to put the comb trough my hair so she had put bathers on for it. she was wearing a casual 1 peice nothing sexual about it and at one point i got an erection and of course i was nude because i was suppost to shower on my own. So she put the comb through my hair and about 20 mins later when she was done i turned off the water and got out but i had gotten an erection and my mother seemd to be somewhat "pleased" with this. not that i should have been looking but her nipples had slightly hardend and it was showing, and when i was drying she had got a glymps at my penis. that night when she came into my room to say goodnight i was again playing xbox and when she hugged me goodnight she put one hand near my penis and squeezed. then she went to bed and since then she has been making small sexual guestures towards me. i have seen my mother nude a few times when ive accidentally walked in on her and she was obviously not happy bout it happening but this is starting to get out of hand now and she has flashed me a few times... how can i make it stop without having to get the authorities involved