Why do I sometimes get picked on like this?

I usually have a lot of friends who I get on really well with but when living with new housemates it seems to be a nightmare! I would get to know everyone in the house, be friendly and yet they will nit pick every little thing I do and try and correct me all the time! Why do I get bullied when I don’t do anything, doesn’t make sense to me, so just want your thoughts as i’m sick of this treatment by others and it keeps happening. I’m fairly a strong character too but not the loudest so don’t understand