But i have not used any mods,i just installed season 3,is it bcz i used mod in season 2?
Yes.
It most likely means that you have Jill path and Bella path open. (Because they wear different costumes if they are on/off your path, it can't deal with it.
If you are familiar with console commands or URM, you can use one of them to turn one of those paths to false.
Or you could delete all your saves & persistent in appdata & games folder and restart game using saves from the OP.
I haven't tried it, but you could also try installing the most recent update of the SAME mod you used in season 1/2 and you might be able to adjust it that way.