Implantation Bleeding Question

Hi, I'm a new member and I have a question about implantation bleeding. I'm 37, have two children and unfortunately had a miscarriage about 7 weeks ago. I've never had implantation bleeding with any of my pregnancies up until this point.
My husband and I are TTC again and I got a positive OPK on Thursday. We had BD'd 4 days before and also that night after my positive OPK. This morning I had pink CM when I wiped that was somewhat sticky, but not egg white...definitely thicker (sorry for TMI). Could it possibly be implantation bleeding if I'm barely 4 DPO? I've been reading conflicting things online. 
Has anyone ever experienced implantation bleeding that early? TIA 😊