Pregnancy test at bc confrontation?

Do doctors make you take a pregnancy test when you talk about bc? I'm 16, my mom recently found out that I was having sex so were talking to my doc about bc in like 3 weeks. I'm like 90% sure I'm pregnant but my period isn't due until tomorrow and I can't know for sure until I take a test, so should I bother buying one or just wait? I mean, if my period hasn't come in 3 weeks obviously something's wrong but I feel like it's a waste if money if I'm going to be tested anyway. So should I?