strangest period?. TMI

Jules
I got my period on the 28th as planned and it was pretty light that day (usually it's a good flow but not out of control). Day two was heavy with the most intense cramping and nausea (I went skiing and had to sit down for an hour and take deep breathes because I was gonna pass out from the pain) after that hour of hell it was okay and occasional cramping here and there. Day three was heavy with occasional cramping and diarrhea. Then all of a sudden it was like dried blood and some pink spotting for three days. 
I'm not sure if this is normal. Usually my periods are heavy throughout, cramping sometimes and diarrhea on the second or third day lasting 5-6 days. I had protected sex 12 days before the 28th and the blood was brown and red the first three days so I don't think it was implantation bleeding but could this be endometriosis or is it just normal?. I don't want to go to the obgyn if I'm just overthinking this all