Have the implant but feeling pregnant

Hi I'm just wanting same advice, I have the implant but I'm feeling pregnant, I've had the implant in since august 2013 and every thing was normal up until 2 weeks ago when I started get pregnancy symptoms, I've never been pregnant before so I'm not sure if Its me or it's just my mind and body playing tricks on me, I've taken 2 tests and both have come up negative, I know you can sometimes put on weight with the implant but I've only notice my breasts are a little bigger and my tummy is a little rounder but the wreid thing is is that I haven't had a period since July which is before I the implant put in, so can anyone help me please.