Bleeding

Hi,

I am very confuse, I have had 3 pregnancies and always conceived straight away. Me and my husband have been trying for 4 months. 7 days before period the tissue was pink when I wiped. 6 d before nothing. I'm due my period in 3 days and first wee this morning there was a darkish mucas blood when wiping and had nothing since. I don't feel pregnant but don't feel like I am about to start my period either as I normally get a bad back and cramps as well as pains down my thigh. Could this be implantation bleed. I took test yesterday but was negative.