Implantation????

I've made several posts since my surgery and I appreciate every response. Sometimes I hate posting cause I feel kinda dumb, but prior to having my tubes tied I never had to keep track of anything. I've never noticed implantation before but now that we're actively ttc I'm trying to learn more about my body and cycles. I'm currently on cycle day 37, af due yesterday, blood test done yesterday showed a 2 for hcg, which is a negative result. the last week I've had sore boobs, headaches, nausea, thrown up, heartburn, and now a horrible backache. I am cramping today pretty bad but not like normal af cramps. I just went to the restroom and got this when I wiped. Normally when af shows its bright red right from the start. I've never actually had anything this light before. and it was accompanied by a creamy cm. Yesterday I was able to locate my cervix and it was pretty low. Today tho it was barely reachable. I ovulated between August 19 and 20th. Last cycle started July 28th. Could I be experiencing implantation now??