What Causes Irregular Periods And Stress Induced Panic Attacks?

Hi I am a 21 year old female who has often had an irregular period (usually every 2 mos. or so I get it) but sometimes it comes earlier. I should have gotten my period around this time, but I don t usually keep track of it because it is so irregular. I had unprotected sex on the 1st of February but he pulled out. I haven t really felt any signs of pregnancy but I have been under extreme levels of stress for the whole month of February and before. I have been having stress induced panic attacks every other day which is something I haven t experienced before. My eating habits and weight also tends to fluctuate slightly. I really believe a lot of this is due to stress, but I cannot help but continue to stress until I get my period, which most likely is exacerbating the problem. I haven t experienced any spotting, cramping (for the most part), tenderness of breasts, or nausea or cravings. I haven t taken a hpt because I am too frightened about the possibility of being pregnant. Should I be more concerned about my missed period? Any advice would be greatly appreciated.