Spotting Implantation?

Hi I'm slightly confused, I came off the pill at the end of October 2015 the last 2 months my periods were a bit all over the place, one month I was a week late but had a normal period, then the following month I only had a 20 day cycle and my period lasted 10 days, very painful cramping, had one day heavy and the rest was light. On an app in which I have about ovulation, it says that I would be ovulating the week after I finished my period, it has been a week after I was fertile and I started spotting last night, very light only when I wiped 🤔 have very tender breasts and nipples, really bad bloating, and constipation, nausea 🙈 What could this be? Implantation or period 🤔 I am not due until 4 days time. Please help