Welcome to the board.
I've never heard of it. Being a Cancer has nothing to do with it though. Have you tried actually charting it? Every time you can't sleep, make a note of the date and see if there really is a pattern on the full Moon. This winter it seemed to either rain or snow every day I had to bring the garbage cans back in from the street. People tend to only remember the times that line up. There were several days it didn't rain or snow when I brought the cans back. There were many days other than garbage days that it rained or snowed. I only really recall the ones that were both garbage day and rainy/snowy days. It's selective.
There may be many nights you did sleep through a full moon, and other nights you couldn't sleep that you don't recall because they were not on the full Moon. The first step would be to take good measurements and get solid data.
I'm Not Evil.
An evil person would do the things that pop into my head.