what should i do?

a few days ago i was in the school bathroom and there was these two girls in my year, who went to the bathroom at saw me come out of the bathroom
since this they come at the end of the break/lunch time and speak about me saying things like ''she's probaly in the toilet'' ''i'm not surprised if she is in the bathroom''
and one of times i came out of the bathroom and one of the girls, was calling her friend to see that im there, and i feel embarrassed
today her friend, said my name and they were waiting to see if i came out of the bathroom which i did, and they were acting surprised and walked away
- i dont understand why they do this, and feel annoyed everytime they do this because its like its against the rules to go to the bathroom