Implantation bleeding or period?

Spotted for 3 days. Brown and pink 
Have had a cold since Thursday don't kno if that means anything 
But I've not had any cramps or anything so how can I tell if it was implantation or period. I can't go by my last period because it's been irregular 
I've also had insomnia, headaches, and heartburn no matter what I eat or drink.