Missed period, negative home pregnancy test, could I be pregnant?

Although I took two pregnancy tests, and both came up negative, I'm still worried that I could be pregnant. My last period was around April 15th, and in May it never came. I'm supposed to be getting my period again today, and it still never came. I have not experienced any kinds of morning sickness, however I frequently get a cramping feeling, almost like my period is going to come but a little worse. Another very noticeable sign that has recently came to my attention is that my nipples have gotten larger. I don't have any darkening or enlargement of the area around my nipple, but my actual nipple has gotten, for the lack of a better term, more plump. My breasts have also gotten larger, and one of my breasts gets very itchy when I take off my bra. I have also been experiencing mood swings, and I've been extra emotional, going from a great mood to on the verge of freaking out in the matter of a minute. Also I've noticed an increase in my vaginal discharge, and more frequent urination. Like I said, I took 2 home pregnancy tests about a week ago and they both came out negative. I need to find out if I'm actually pregnant or if something else is happening to my body. I'm only 16, and my boyfriend is 17 so going to the doctor is out of the question for now. We have never used a condom, and have been sexually active for 6 months now. I am, however on birth control and have been for 2 years. If anyone could offer me any knowledge or advice it would be extremely appreciated! Thank you!