bleeding and pregnancy

My husband and I have been TTC, but only recently decided. This is my first month off birth control and I monitored my CM and mapped out my most fertile days. My most fertile day was the 15 so we were intimate the few days before hand and on that day. I started bleeding the 16th, however, which seems early for implantation bleeding so I was convinced I had my period even though it's not due until the 27th. I started using tampons but there are no clots in the blood like I usually have during my period and there is barely even any blood I only need one tampon a day and even then there isn't much there. The blood is mostly brown and pink, but it's been about 4 days now, which also seems long for implantation bleeding. It's too early to test, but I was just curious what people thought?