I am on the implanon birth control. I have been for about 5 months. Periods usually last between 3-5 days. This month I have not bleed. I had dark brownish when wiping and the bright red 2 days ago but then nothing else. I have felt nauseous and lower back pain. I had unprotected sex about 2.5 weeks ago. Could I be pregnant?

You could be I mean there is a slim chance of pregnancy while on birth control but there are also other things that can cause those symptoms so I would wait a couple weeks and take a pregnancy test but either way if the symptoms continue I would see a Doctor.

I will agree, since you are having sex, there is a chance, no birth control is 100 percent and pregnancy while using this happens.

At this point wait about 2 weeks and take a pregnancy test. ( use first urine of the morning)