Just before you are due to get your periods, you really should not be worried about the possibility of a pregnancy as technically speaking you should be post-ovulation when the risk of fertilization is lowest. More so given the fact that no ejaculation took place inside your vagina and hence you had no contact with the sperms, it is highly unlikely that you could be pregnant.
Precum or pre-ejaculatory fluid rarely contains any sperms and these sperms usually are incapacitated and cannot get anyone pregnant. I believe there is no reason you should worry about the possibility of a pregnancy. If however you still feel that you wish to confirm the same, you may do so by taking a home pregnancy test.
A home pregnancy test is a urinary hCG- based test and is 99% reliable in detecting a pregnancy. It is best to carefully follow the instructions on the pack for accurate results.
In the future, please use some form of contraception. There is no use worrying about something that is best prevented. Equip yourself with the knowledge of various contraceptive options available to you especially that of emergency contraception to avoid such stressful moments in the future.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.