I'm super stressed!!

I had sex with my boyfriend at Dec 11, we used condom. My period is due on Dec 26 but I'm 3 days late and having clear discharge. That clear discharge starts to feel like I'm on my period. I show no symptoms of pregnancy but I kept thinking I might be pregnant. I cry whenever I think that I'm pregnant. I'M STILL 17!! My mom will kill me if she see the pregnancy test so I can't buy it.🤧 What should I do? Myabe my period is late because I'm stress?