Should I worry?

So I was supposed to start my period yesterday, but last month I switched my birth control from the pill to the nexplanon implant. I know that some people don’t get periods but I didn’t know that they would stop immediately. I only had sex once and we used a condom the whole time so I don’t think I got pregnant. I took a test yesterday morning and it was negative. Am I just going to be one of those people that doesn’t get a period or spotting? Does that mean my birth control is working. I had sex again for the second time last night and we had a little mishap where I think precum got on the outside of the condom before we started having intercourse and I’m just worried cus I really don’t want to get pregnant