Help please?!?!?! is this normal?

So 2 and a half years ago, during summer, I had some yellowish discharge and the doctor said I would get my period three years from then, now like 4-5 months ago the discharge started to get more yellowish then it just stopped about 3 and a half months ago. I'm always really scared it might just randomly start while I'm at school and seep through my pants, so I wear a pantiliner everyda but im still really scared about it and I can't stop thinking that suddenly I might get it and be really mortified, why is this stuff happening?