Trying to conceive just had baby 2 months ago

Okay I've haven't had my period yet since I had vaginal birth; me and my fiancé are trying to have another baby. We started three weeks ago, I'm currently breastfeeding but I do use a paci and we haven't had night time feeds since she was two weeks old. About two weeks ago I started having cervical mucus that was wet and slippery and we had sex since then I've had an abundance of different cervical fluid from thick to creamy to sticky to wet again, I'm going crazy trying to figure out if I ovulated. I took a first response pregnancy test yesterday and it was negative. Also the past two nights I had a small spot of blood on the toilet paper after we had sex, it was a small pink spot. I have never ever bled before in my life after having sex and now it's been two nights in a row with a small tiny spec. Can that be implantation bleeding? Is it possible I ovulated later than I thought? Help!