Generally you shouldn't take a home pregnancy test until your period is late. In most cases it takes about 2 weeks from fertilization for implantation to occur, and then another few days for there to be enough hCG to even show up, so it usually just better to wait, since you don't know exactly when those processes actually occur.
If you used protection properly you should be safe. However, if you are worrying about pregnancy then maybe you should not be having sex. Sex can have many risks and you should become educated about those risks. Being educated about sex will help you make the right choices for yourself. Always use protection to decrease that risk and have a plan if you do get pregnant. Any guy that truly cares will use a condom and if they won't tell them to piss off. You have to look out for yourself.