Period or implantation bleeding?

Based on my dates in my tracker my period shouldn't have been due for another few days. Yesterday at work I had lower back and abdo pain milder than usual cramps. Went to the bathroom and thought I'd started my period but it's not like normal red red it's brown and pink/watery red. Now on day 2 of what I thought was period and there's literally like 2 spot on a pad and then only when I wipe nothing like my usual period for day 2 what I'm getting is almost like the end of my period. We did BD on the 3rd which is when I got a peak LH test so around the right time for me to have ovulated. I did a cheapy test at estimated 10dpo but was negative. I've ordered a first response one but not sure if I should take it or not or just wait and see if my period behaves.