I have the implanon birth control since december 2010. I think I may be pregnant, if the hpt cone back positive, how soon do I have to get it out?

Soon. If you are pregnant, you should get it out as soon as you can. The baby is not likely to have any bad effects from the Progesterone in implanon, but the medication alters the normal hormonal balance so could negatively affect the pregnancy. Implanon is a pretty reliable method of birth control, so it's unlikely (but not impossible) that you are pregnant.