implantation-or-period

I had sex on day 15 of my cycle..we finished using protection.. I have a regular 28 day cycle give or take a day either side. On cycle day 25 I started having tiny streaks of blood in discharge only when wiping, the following day it was very pale brown discharge no blood, by day 27 it was a couple of spots of pinky spotting brown again.. by now I assumed my period would be there on time but period due date and it was nothing just a little mucous light brown.. morning day 29 I had bright red blood when I wiped nothing else, no flow. Later that day I felt a trickle and didn’t check til later when I got home and I had more blood not a huge amount. Later that night I have moreof a flow but it only seems to be when I go to the toilet and no clots all just bright red watery blood.. toilet water looked red. I assumed my period was starting so I counted it as day 1, for day two it was pretty much blood not real heavy it somewhat had been more stretchy like thicker but I was only using a pad two max in a day. Today is day 3 and there is nothing only brown which was quite dark. When wiping it was dark brown like mucous. Like as if finishing my period.. is this just a really short period? Does it sound normal? I use to have heavy 4-7 day period and now short.. is this normal? I also had lots of gas the week prior and constantly needing to poop. Headaches, really moody, I was feeling pressure in my lower abdomen too a fair bit and sharp twingey pains on both sides particularly leading up to and the day I had bleeding. Just want to know is it normal or am I being crazy.. thanks