Implantation

I have a very irregular period. I had one Jan 6-9 (very heavy), Jan 28- Feb 2 (very heavy). According to my tracker and how I've been ovulating, I ovulated on the last day of my period (Feb 2). I also had unprotected sex and the guy came in me. Feb 6-7 I had unprotected sex and the guy came in me 3 more times. I've been very nauseous, dizzy, a tugging feeling in be abdominal area, and tired. Today I had watery discharge and light pink spotting with one clump. I'm supposed to ovulate again tomorrow (Feb 10) and start my period on Feb 17. Now my back is killing me. Could this be implantation bleeding?