When am I supposed to test??

ok so I'm only 16 and my periods are usually on track every month if they're early or late it's like by one day. but I'm almost a whole week late, which almost never happens. Before I have my period I always have really bad cramps leading up to "my time of the month" but I'm a week late and don't have any symptoms of is starting anytime soon. the only thing that's different is that my boobs are extremely sore. I am sexually active with my boyfriend and I know you aren't just supposed to test at random times so I was wondering when the best time for me to take a pregnancy test would be. can anyone help me?