Well you need to test in 2-3 weeks. In the future leave the condom on, if it's coming off you may be using it wrong.
It means you could have very well had sex during the days when you are most likely to ovulate which increases your chances of getting pregnant. I would say if you had unprotected sex you do have a chance of being pregnant this month. I would say that if your period is late than take a test. It would be way too early to take one now. Good luck and I hope everything turns out ok.
Any time you have unprotected sex, especially around ovulation, you can get pregnant. So wait two weeks and take an hpt.