Pregnant or missed ovulation?

Stopped 'the pill' after taking it for 3yrs. 
Had a normal period. 
4 weeks later had another normal period. 
A week later I bleed for 3days.
7 weeks later (yesterday) I took a pregnancy test and it was negative. (today) I got my period.
Not sure if it's implantation bleeding/spotting or it's a period. It's pretty heavy. I had bad cramps and mood swings. 
Advice?