Periods on implanon.

How many periods have you had while taking Inplanon? I got it early October and so far I've only had one. I know that it's very effective for preventing pregnancy. But I can't help but feel uneasy when I don't have a period, even though that's like the main side effect. I've never been pregnant so I wouldn't even know what signs to look for even if I was somehow. I guess I'm just looking for some reassurance to ease my mind.