Implantation bleeding?

I started AF 3/3. On 3/18 I started spotting very light. On 3/19- midday 3/20 it was a little heavier and by 3/21 it was very light spotting in the morning. I've read IB is very light and only lasts 1-2days. I also have read IB can last up to 4days. Any thoughts?