Stress, and sudden weight loss/gain can delay your period. You're not pregnant Hun its stress.
Hmm, now thinking about it, i have been very stressed out lately and i'm trying to lose a few pounds by summer so i have been eating a bit less, and healthier. I'm hoping nothing too major is going on, thank you very much for your response it helped alot!
During your teens and early 20s your periods are likely to be irregular, your hormones are still getting regulated and a lot of things can interfere, from stress to diet changes to anything really. Since you're not sexually active I wouldn't worry about it much, if you go more than a couple months without one it's worth a trip to the doctor though.