birth control shot

I've been on the depo birth control shot since august of 2016, I'm coming up on I think it's my 4th shot ? But I noticed that my period has been absent for a while now. I know your period is supposed to be irregular on the shot and eventually most people loose their period all together but I don't know if it's too soon for it to be gone... I'm worried please tell me I'm okay 😂