Possible to ovulate early?

Yesterday I had a follow up with my RE to check my lining due to previous appointments it being thicker than usual. Mind you I just finished my cycle so I was CD8 yesterday and my RE said my lining is already really thick and that I possibly ovulated already. I just don't see how that's possible since I finished my cycle on CD6. I'm very frustrated, I'm doing bloodwork today and a hysteroscopy tomorrow. This is the first time this has happened as my OPKs show I ovulate around CD13-14 each month since my miscarriage.