Weird period I think?

Hi all.
So, my period was supposed to start 13dpo, but nothing happens. Took a test on 15dpo and came back negative and then when I wiped noticed a small dot of pink cm, so I figured af was just late. Put a tampon in and went about my day. 
Later in the morning I took the tampon out and there was barely anything on it and when I wiped..nothing. Kept a panty liner just to be sure but nothing.
The next day mid-morning I had a gush of heavy bleeding but it only lasted a day and now I'm back to nothing. My period has never started as spotting and has never lasted shorter than 4days. Could it be possible to IB or was it af?