Pre-ejaculate can contain sperm, and it's something that (especially during penetrative activities) usually goes unnoticed by both partners. The vagina is a wet environment, so you are not going to be able to feel the addition of some extra fluid. And (no matter what a partner may claim) men generally do not feel pre-ejaculate when it happens (they may feel the wetness later, but there is no sensation associated with it actually coming out of the penis) nor are they going to be able to notice it during penetrative activities where (again) things are already lubricated. Pre-ejaculate can occur throughout the course of any erection, so it is always safe to assume that it is present. Also, many men (especially younger men) may not be able to "pull out" before ejaculation actually starts (even if they think they managed to withdrawal, they actually may not have).
According to our What's the Risk? Easy Pregnancy Risk Assessments
If you DID have unprotected penis-in-vagina intercourse but the man DID NOT ejaculate, then you have a LOW TO MODERATE risk of pregnancy. If it has been less than 120 hours since your risk, you may obtain emergency contraception. If it has been greater than 10 days since your risk, see your health care provider as soon as possible for a pregnancy test and an STI screening.
At this point, if your period is late, you should take a pregnancy test because you definitely had a pregnancy risk from this contact. You can buy a home pregnancy test at your local drugstore/chemist/grocery store/chain store. Make sure that it is not over it's expiration date and follow the directions on the box. Since your period is late you should be able to expect an accurate result. You can also take a test now and then wait a week and re-test to verify the results. If your period still doesn't show up, you should go ahead and call your doctor. Since you had unprotected contact, you will want to call your doctor anyway to schedule a full STI screening. You can also speak to your health care provider about finding a method of birth control that will work well with your lifestyle. Condoms are easy and are the only contraceptive that also provides STI protection, so they are an excellent choice. But you can also ask about other methods that require a prescription, if you would like.
Are there other things that can cause a period to be late? Sure. Stress, weight changes, major health changes, etc. can all cause late periods. But since you have had a pregnancy risk here, that is definitely a possibility as well.
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