AITA for taking off my clothes when my SIL started changing in front of me?

SIL was getting ready to go out and she started changing in front of me. I’m a very awkward person so I didn’t know what to do. She asked me “why are you taking off your clothes? What the hell is wrong with you?”. I told her I’m just getting comfortable and she got pissed off. She told me I was being a creep. She called my SO and I got in huge trouble. I don’t see how I was in the wrong here?