I had unprotected sex about a month ago and i wasn't in any contact of sperm. my period came 3 days early and lasted 3 days. should i be worried about?

Should be ok: However a pregnancy test could be reassuring for you. Please consider a safer and more effective birth control plan, consult your doctor.

Infection: You need not worry about pregnancy, though you may wish to do a home pregnancy test in a few days. However, you are at risk of having sexually transmitted infection and may wish to consult your doctor. If you do not wish to be pregnant, use contraception all the time, every time. You may consider implanted contraceptive, or IUD. Practice safe sex if you have sex. Get HPV vaccine, if you are younger than 27 years.