I'm worried..

So went to the doctor, to see if I am pregnant. haven't gotten my period since september 20th. my period is 30 days late, they also tested for STD's I dont think I have any considering I've had no symptoms. I've had some pregnancy symptoms such as tender brests, some nausea, and of course the biggest and easiest one missed period. do you think it could be an std, or am I pregnant? What else could be going on with me