Is it normal my mother behaviour

I am 27 male from south asian country. I really dont know the behaviour of my mother is acceptable or normal. Since i was 10 my dad works in overseas and come home every 6months or so. My mother is 44 now, dark, medium built and she is loving and caring.

Since i was 11 i was confused with my mother's behaviour. those days i go to bed early around 7.30 night. our house is small and we sleep in one room. i woke up once when i was 11(12yrs ago) around 11pm and heard some moaning sound, the light was dim. i saw a male was enjoying with her. THose days i didnt know about sex, but now i can realise that. they didnt realise i was awake and saw them. finally that guy left from there around 1am.

like that time to time i saw different males came to her in night time and enjoy with her.
When dad came home from overseas she acts like she loves him only and didnt do these things(unless she does outside)

Time goes on and i was with studies busy, couple of years ago we moved to city area since i got a job here and no one know us. she also put on some weights. the thing is she has changed with her dressing way, she wears very short loose dress or skirts 10-13inches above. since we live in a flat, sometimes she doesnt bother changing dress infront of me and stand infront of me with her lace bra and lace/transparent g-string. sometimes she doesnt even care when she sits in sofa or chair let visible her g-string through her short dress. one day afternoon i came to flat due to i was sick and shock to see, she was enjoying with 2males in same time, all naked she seems enjoying. i just walked away.

for the past 8months she mostly came home late or sometimes next day morning. she says she goes to friends. However i followed her one night and saw she was going to a hotel. later found she was hanging out with a foreigner. I realised she visits hotel often, more like she is selling her body.

she is nice with me and i am scary to ask. Should i ask what she doing or leave it as is.. Is it normal what she is doing