If you got a positive, you are pregnant, CONGRATULATIONS!!! (There are falso positives, but very very very weird). I knew I was pregnant 3 weeks after my LMP. I think it depends on when you ovulated, it might be earlier than you think. Very accurate pregnancy tests will be positive about one week after ovulation.
My period was jan 31st, I just knew I was preg bc I was having bad headache/dizziness a few days prior to testing. I had a small spot of blood on my pantyliner on feb 20th. I tested positive on feb 21st.
Implantation bleeding is very short so make sure your not bleeding long bc it could be a sign of miscarriage/chemical preg. Congrats!