Advice please :)

Hi all , was wondering if anybody could offer a bit of advice or if anyone is in a similar situation - I had the implant  fitted 18 months ago- my periods were ways irregular before this , after having the implant fitted I had on regular clockwork period each month and have done for the 18 months I have had the implant . However I have no not had a period for the last 3 months, I'm experiencing all symptoms of pregnancy, toilet frequently headaches feeling nauseas sore tender swollen breasts. I know these can all be side effects from the implants but can they just start 18 months after having the implant as have never had them since having the implant in so far until now. I know it's a very slim chance of pregnancy  with this form of contraception but do have a friend who fell pregnant on this implant so know it can happen. Any advice much appreciated thank you