Not getting pregnant after birth control?

So I had got nexplanon implant a form of birth control and I had it for 2and a half years.. Well back in August I got it taken out and have been trying to convince ever sense but no luck still and its been 8months of trying and I'm afraid I can't get pregnant.. I was told by the doctor I would be able to be prego right after the implant was taken out and that's not the case .. I had a check up to see if I was ok and the doctor said I was fine but why have I not gotten pregnant yet ?