I'm Currently On Implanon And I Don't Use Condoms With

I'm currently on implanon and I don't use condoms with my boyfriend. 2 days before I got the implant my boyfriend had an organism inside me. I took a pregnant test at the obgyn and it was negative. Was it to early ? Also I've been smoking a lot and I haven't gotten my period since I got the implant. 3 months ago. But I've been spotting. Could I be pregnant ?