Next FET after Chemical?

My FET is ending in a chemical so I’m stopping estrogen & progesterone today. My HCG is dropping quickly and was told to expect my period in a week or so. My REI is out this wk and the RN isn’t willing to say much.

Curious how soon after a chemical you were able to start your next FET cycle? Did it start immediately w the first period or did you have to wait for a full normal cycle before you could start?