Nexplanon (?)

Alrighty so to start this off I am a seventeen year old virgin who got the nexplanon implant just over a month ago to help relieve severe period symptoms and also if I ever do decide to have sex I'd rather be safe that sorry. But I was on the last day of my period when I got the implant inserted, is it normal to not have another period again afterwards or am I just maybe overreacting? I had one bad cramp and a little bit of blood but it was brown and older so I assumed at the time that period was starting (I was wrong) it's been about a week since then and I have yet to get my once very normal and regular (albeit painful) period. Is this a common occurance or am I reacting badly to the nexplanon? I dont really know whats going on anymore and no I don't have any female adults in the picture so I can't really ask them. Pls help me :,)