These are the symptoms that I have had on and off for about 2 weeks, and I missed my last period, but my periods have been a little irregular, nausea , abdominal pain ( just a few times), a little cramping. I am 18 years old and became sexually active at the beginning of August. I was put on birth control pills a year and a half ago for a ovarian cyst , but quit taking them a year ago because they messed up my hormones.