Stomach sleeping... swaddle?

I caught my 6 week old sleeping on her stomach tonight. Since she was born she has always slept on her side and we swaddle as this is the only way she will sleep. Tonight she was laying chest down with arms under chest but with her hips/legs to the side. Her face was sideways and not in the mattress so she could breath just fine. I had to put her back on her side twice. My question is do I still swaddle? I’m scared to go back to sleep. Time to start the transition? She can’t roll over yet and can’t keep her head up for that long without help.