can cause side effects like nausea, menstrual irregularities, breast tenderness etc because of hormonal effect, but as you are having somewhat severe symptoms better to consult gynecologist once and take tablets for controlling the bleeding, analgesics and anti emetics etc, if your symptoms do not subside with these you can go for removal of implanon with your doctor's advice.
if you started implanon during your menstrual period then there is less chance for pregnancy
, but if you started after menstruation
and had intercourse around the time of ovulation then better to go for blood test
for pregnancy once.