Implantation Bleeding Question

Le

This may sound like a dumb question and I'm sorry... but I was just wondering, you don't have to have implantation bleeding to be pregnant do you? I'm on 8 DPO and I have had a small headache that isn't shifting, I feel slightly nauseous after my food, my breasts are tender to the touch and all I want to do is nap.... Could I be pregnant and not experience any implantation bleeding? thanks in advance