Anyone else had this experience?

Let me start off by saying hi! I am new here and happy to have others I can talk to about these types of things, so thank you all in advance <3 
Also, I apologize for the lengthy question, but I'm not sure what aspects are relevant and what arent:
So, I am pretty regular with my periods. When I was younger, they used to be horrible and went on for 2.5 weeks, and would come back every 1.5-2 weeks. I went on birth control for 3-4 years, and stopped about a year ago (I felt like no matter what kind I tried, they all made me feel crazy). Since then, my periods have been way more pleasant and very regular, pretty much like clockwork. 1.5 weeks long, (7 days bleeding, 2-3 spotting), with about 3 weeks in between. 
However, this month, my period came a week early and was definitely way different then I have EVER had it! 1st day was a little spotting at night, 2nd was a medium flow (went through 2 "super" tampons for the 12-16 hours or so I had them in) next day was a light flow, then the next (4th day) was just very light spotting that ended in the morning. I also had unprotected sex that day with my S.O. 
After that, I had two "clear" days, with unprotected sex again on the second day.  This led to spotting the next day (yesterday) for a few hours, and nothing so far today. I have been checking my CM during this time, and immediately after the "early period", it was the consistency of egg whites, and very thick and a lot of it. Now, it is definitely thinner, still sticky, but not as much. My cervix also feels slightly firm, but almost like it's swollen and closed compared to the "egg white CM" day (I just recently started tracking CM, so I'm still not familiar with what is my norm). My "regular" period should have come about today. 
I have also been experiencing mild nausea on and off for the past week and a half, even throwing up a few mornings last week. In addition to extreme fatigue, and headaches (which I NEVER get). And on the day before I started spotting again, I was getting moderately painful cramps, which is also unusual for me.
Has anyone else had this experience? I have been testing for pregnancy, but only at night (it ends up being when I have time) and two days ago was my last test with a negative. So now I'm confused as to what else could be going on? 
I apologize for the long post again! But I greatly appreciate your time and responses <3 thank you ladies!!!