I had unprotected sex when i came off my cycle took a plan b the next around 9 had unprotected sex again the next day or two no plan b

First week of the month was experiencing spotting for three days boobs sore cycle was supposed to come on next week didn’t come

On the 18th went to the doctor negative test but at the end of the moth experienced mild cramps out of nowhere cycle was on heavy to light then stop but then on my 3rd night around 9 until 4:42 that morning i was spotting no full pad it was very light

Took a pregnancy test later on i a couple of weeks and the line was faded but nothing in the control window ?

I talked to a doctor and she was like i might be experiencing implantation bleeding and my mom told me also that she went through implantation bleeding up until 3 months ?