What Causes Light Bleeding,cramps And Lower Abdominal Pain During Periods?

Ok so I am currently on my third day of my period. First I d like to say that my period was actually suppose to start today but, it started on Sunday. When it started my period blood was light pink and it had mucus in it. I spotted for a few hours before I actually started. That s really not normal for me. What s normal for me is I start bleeding right away once I notice my period when I go to the bathroom. So when I actually started flowing it was a light flow not extremely heavy. And when the blood changed to it s normal color it was mucus and a reddish mixture. I have more tissue then normal. And the cramps when they come is more of an ache on my left side which would be your right if you were standing in front of me. Like today the ach was in that spot but next to my belly button. Yesterday I had a ache and that time it was in my lower abdomen on my right ovaries. i noticed all day when I would go to the restroom that the blood was gritty. Mind you my flow never got heavier or anything. Like I am not spotting but it s not heavy either if that makes sence.also when I started my period blood was a darker pink it didn t turn red until yesterday.