What Causes Cramps,constant Headache,mood Swings And Delay In Periods?

i am 19 and i have been trying to get pregnant for 5 months. for the past few days i have been experiencing constant headaches, horrible mood swings, everytime i smoke i feel sick, tired more, and often breast cramps. im not saposed to start my period for 2 more weeks, and today i started bleeding. and whats even more weird is that normally when i start my period i will have cramps starting a few days before. but no cramps this time. do you think i could be pregnant?