Implantation bleeding?

My fiancee and I have just started trying last month. My period usually comes around the 22nd-23rd. This month I have been having cramping, headaches, and fatigue. I shouldn't have started my period until today but I started bleeding on the 18th and it lasted until the 20th. I've read that most women who have implantation bleeding it's usually very light but some have heavy bleeding. Mine was heavy but not like my period, and my period usually last 5 days. I took a rest yesterday morning in but it was negative. I also read that you should wait a couple days after implantation bleeding to take a test bc your placenta hasn't produced the hcg horomone. Anybody else have this? Is it implantation bleeding?