??? Help???

Okay so my boyfriend might’ve came inside me like 3 weeks ago but yesterday I had like light bleeding and I’m scared can implantation bleeding happen 3 weeks after unprotected sex? (When I bled We had just had sex like 2 hours before but I NEVER bleed during sex like even super rough sex lol) and we’ve been having sex for like 2 years now, I’m barely 19 I’m irregular and we had sex right after my period ended so I’m scared, I took two test last week on Saturday but they were negative probably too early

I’m not scared to have the baby I just need to know cause I work in radiology and I can’t work there if I’m pregnant and I wouldn’t want to harm the baby in any way