Spotting !? Ovulation spotting or implantation bleeding!?

Okay. So I have really irregular periods. My last three cycles were December 1-4, September 21-24, and July 29-aug 4.

I have never had spotting before in my life (not even with my first pregnancy) however, I had spotting for the first time that lasted two days (Wednesday, January 10, and Thursday, January 11) the spotting was very light and only noticeable when I wiped. I had unprotected sex on January 7.

According to my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> apps I should have ovulated last night (I usually know when I’m ovulating but never noticed it?)

However where my periods are so sporadic I don’t know if the tracker is accurate. My period usually never comes when it’s “expected” to.

So the spotting was brown/pink, and accompanied by brown “sticky/gooey” discharge. I had lower back pains on and off since Wednesday, I’m always warm but mostly in the morning which is odd for me as I’m usually freezing all the time. I’ve had headaches here and there, barely any appetite (not nauseous, just not hungry), I’ve been a little bloated and gassy, and I’ve had the worst time sleeping, I’m constantly waking up throughout the night for no reason.

I took a pregnancy test yesterday morning which came back negative.

Any insight as to what’s going on?