no period on Skyla

Kali
So I got my Skyla put in October 4th still no period. I have only spotted once and that was for barely a day. Nothing after that. I Didn't get my period either, so I took 2 pregnancy tests both came back negative. Should I be worried or is this normal. I like not having my period but I'm sexually active so I'm happy with getting it once a month to know I'm not pregnant.