I have bouts of depression but I get over it. Is it possible that its not depression but an hormone imbalance due to the contraceptive implant in my a?

Possible . Depression has many causes-- it can run in families, it can be caused by hormonal imbalances ( not just estrogen/progesterone) but also thyroid and vitamin d, as well as some variations that are caused by the change of light. There are also social and psychological causes. Whatever the cause, if you feel down for two weeks, or feel like hurting yourself, definitely see your doctor.
Could be. Progestin only contraceptive implants imitate a state that is similar to mild menopause. A woman's estrogen level can be very low while using an implant. Some people experience low estrogen levels as a change in mood or energy. One way to see if this is a factor, is to ask a doctor to give you an estrogen boost for a short while and see how it feels. For example birth control pills.