Period Started.11/16/16.had Sex Day Or 2 After Period Stopped.he Did

Period started.11/16/16.had sex day or 2 after period stopped.he did ejaculate inside me.I took aftera 54 hours later.then 5 days later(today) I had about a teaspoon of bright red blood with very small amount of what I assume is tissue.then I went to bathroom and whipped and a minut amount of bright red blood.implantation or aftera pill side effects?.also slight back pain I don't normally cramp much during period.also yesterday I felt what I thought was bubbles very low in pelvic area but have been slightly gassy.I am having super mild discomfort in lower pelvic very very mild.