Period 2 weeks late. not had sex messed around with bf. no way any sperm was able to get in. did travel, uni stress, prolonged cold, bad sleep. help!

Mutiple factors: can delay your cycle: stress, tension, illness, hormonal variations, changes in climate/altitide. I suggest keeping a menstrual diary indicating the (s)-start, e-(end) sp-( spotting) h-(heavy), l-(light) or c (clotting). This will be helpful to both you and your GYN. Nonetheless, consider condoms or BC pills plus spericidal foam or gel.