Ttc after miscarriage before period

I’m currently going through my 3rd miscarriage and wanted everyone’s opinions/experiences with getting pregnant before having a period after a miscarriage. With my past 2 miscarriages I have always been told to wait to have 1 period before ttc again as if I didn’t I would end up miscarrying again as there would still be parts of the previous miscarriage in my body. Is this actually true or has anyone had a successful pregnancy conceiving before a period? I have PCOS and don’t really want to be waiting for another period as I’m uncertain when it will be. Also when is it safe to start having sex again after a miscarriage?