Heather Corinna replies:
I have been sexually active for about 3 months now. Usually before sex, my partner and I have a few minutes of unprotected sex and then he puts a condom on. My period is now a week late and I'm worried. I already took a test that came out negative but I'm still kinda scared. My friend told me that it's usual for my period to not come when first having sex. Is this true or should I wait a little while and retake a test?
Condoms are ONLY reliable birth control when they are used for ALL direct genital contact, from start to finish.
If you have intercourse without a condom, and only put a condom on later on, then you can't depend on condoms to protect you against pregnancy (or STIs), since it is possible for pre-ejaculatory fluid to create a pregnancy.
Too, starting sexual activity or intercourse doesn't have the power to alter the menstrual cycle, unless there is a pregnancy or infection (and even then, with the latter, one rarely sees menstrual changes). Now, stress -- or more accurately, the changes in people's behaviours due to stress -- can delay a period, and a lot of women get very stressed out by sex, especially if they're taking risks with it, so that's possible, but intercourse itself can't delay a period unless it has caused pregnancy.
If your risk was more than 2 weeks ago when you took the test, you can rely on the results of your test, so long as you took it and read it correctly. You can also retest in a few days just in case, or if you did take the test too soon. If you retest, and it's not taken too early, with two negative results, you really can rest assured that you are not pregnant.
However, since you've been having some unprotected sex, I'd suggest that you go into your OB/GYN or sexual healthcare clinic if you are not current with your STI screens anyway (as should your partner), and you can also ask for another pregnancy test there, and to have them just check in to be sure everything is okay with you. Once you get all that covered, if the result is not pregnant, no STIs and no other issues, then your best bet is just to try and relax and accept that now and then, our cycles can be unpredictable, and that's okay.
Obviously, from now on, if you're going to use condoms as your birth control method, you're going to want to start using them properly, which means for ALL contact. If the reason you two haven't been doing so is a sensation issue, be sure you're also using plenty of latex-safe lubricant with your condoms. A drop inside the condom before he puts it on makes things loads better for your partner, and plenty on the outside, or rubbed unto your vulva, will improve things for you, as well as keeping your condoms from breaking.