The arm implant

So I have had the nexplanon for exactly a month now. My period was due to start on Monday but it hasn’t came yet. I know that some people don’t get periods when on the implant but I didn’t know that it would take it away immediately. Before the implant, I was on the pill and had very light periods, but it was still there. I took a test this morning and it was negative. I’m starting to get nervous but I don’t think there is anyway I could be pregnant. If I’m not getting my period or any spotting, does that mean that my implant is working?