TTC- AF or IP

My SO & I are TTC. I went off of birth control in January and this is the first cycle for trying. We had sex March 20, 21, 22. I’m pretty sure I ovulated the 21. My LMP was March 5 and my next one is due April 5. The night of the 28th I had some really bad uterine cramps and on the 29th I had some light pink bleeding start. This morning I woke up and it’s gotten heavier and darker but it has lightened up throughout the day. Could it still be implantation bleeding? Or did AF come 6 days early?