What Causes Lower Abdominal Pain And Vaginal Spotting While On Nexplanon?

Hi ihave nexplanon had it dince november 2014 after giving birth in october had a period in december which was heavy and ladted 12 days and havent had one since had abit if spotting in january which was pink in couler and lasted about an hour have alot of pains in my lower abdomen fee like im gunna come on but nothing feeling sick tierd bloted dizzy have alot of gas since having implant cud i be pregnant or is it side affects