I agree with both of the posts above. It really could be anything - including something like stress which is not a big deal. I would also like to know if you are normally regular? I ask this because my periods were always slightly irregular growing up, but nothing too crazy. Then all of a sudden I was going months at a time without one. It took me two doctors before I was finally diagnosed with PCOS (polycystic ovarian syndrome). Docs kept telling me I was too skinny and wouldn't bother checking (until I started packing it on!) - meanwhile I come to find out that 40% of women with PCOS don't even have weight gain! If your periods have always been perfectly regular and on the money, I wouldn't worry too much about it. But if you are not pregnant or overexercising and they aren't completely regular, then it may be worth looking into, in addition to having your thyroid checked. If you want to find out more about what can cause it, the proper medical term (which I never heard until it started happening to me) is "amenorrhea" - if you google it you can get all kinds of info.
Good luck to you - I hope it's nothing serious :o)
So did you get your period, but 6 weeks late? If so, there could be many reasons for that. Sometimes ovulation is delayed and when that happens, your period will be delayed too. It could be because of stress, too much exercise...or you could have been pregnant and had an early miscarriage (but if it was a miscarriage, I think you would have known). There are a number of other reasons too why ovulation is delayed sometimes. Are your cycles normally regular?
obviously u could be pregnant. if u r single then it meight be cos fo hormone disorder. Do pregnancy test at home.