Safe to say I'm not pregnant? Thought you ladies may know more since you've been through it

So I had a period June 11th (I usually have irregular periods and don't know when they'll come) but then I started bleeding July 11th, I went to the doctors and got a hcg blood test that same day, negative. I waned to rule out if it was implantation or period. I then thought I'd test again the 31st to see using a hpt test. It was negative again. If the bleeding was implantation would it have showed up positive by then???  Is it safe to say I'm not pregnant? Thanks ladies!