Well it depends on your cycle, how long it is etc. but if we say that your cycle is the average 28 days, it would mean that you were at your most fertile when you had sex! The fact that you are still young could mean that your periods are still a little irregular and you could ovulate later or earlier in your cycle. Even still I think that having sex at that point in your cycle is in the danger zone.
How long ago was it that you had sex? if it was less than 3 days ago you can get medication from the doctor ( in the UK you can buy it from a pharmacy, don't know about other countries ) this medication will stop you becoming pregnant but it has to be taken within 72 hours of unprotected sex, the sooner the better.
If you know when your period is due you could wait until the time you would be expecting a period and take a test then, don't take a test to early as it takes a few weeks for hormone levels to get high enough to show on the test, you don't want it to be negative if really a few days later it would be positive.
It's great that you used a condom to protect yourselves from pregnancy and sti's but accidents do unfortunately happen and women have become pregnant because of a condom splitting, if you and your boyfriend are going to be having regular sex you need to think of another method of contraception as well as a condom to be extra safe, such as the pill, the contraceptive implant or inter uterine device.
I hope things work out ok for you.
The time your most fertile is the week after your period.