Could i be pregnant?

Ok, so me and my boyfriend have been having for just under a year now. We ALWAYS use a condom. Anyway, my period is usually due around the 13th. I had one in december but have missed both january and february. I have been under a lot of stress since before christmas, new job, family members severly ill and close to death. Would this stress have affected it? I have had a regular period since about the age of 10 and a half, i am now 17 and a half. Please help.