cramps in back & stomach, pee a lot, pregnant?

i am 24 yrs old and all my life my cycle has been on time full force for the first 3 days without missing a beat until it changed the expectancy date of it when i was 23. my usual menstrual length is 6-7 days and i know exactly how it will start and end. for the past 4 or 5 periods i would have pains in my right breast one week before my cycle would show and that let me know that uh-oh it's coming. my period comes 19-20 days apart all the time but in november it didn't do that. a week before there were no usual signs of it coming but since i mark my calendar i knew it was to come on nov. 22 or 23. the day before Thanksgiving i woke up at 7a.m. to get ready for work and i felt horrible. on my way to work my stomach was aching and i thought it was gas because i had a bowl of cereal the night before and milk doesn't agree with me. so while at work i felt bad and i made it through, rushed home to take a shower and i tried to relax on the couch. all while lying down i couldn't get comfortable, i had pains shooting all in my back and stomach and i had no fever or diahrreah so it wasnt the one day flu. from 3p.m to 6p.m. i threw up 5 times and i couldn't even hold water or ginger ale on my stomach. the vomit was dark yellow but clear and it was bitter. i couldn't eat that night but the next day i was fine but with no period. on the 23rd there was no period either. i didn't panic i just took it for what it was. i had heartburn, i constantly belch after drinking even a little bit of water, by breast are not normal feeling i have had horrible cramps in my back and stomach, i pee a lot off of one cup of water, my bowel movements don't move like they used too, i have had slight headaches but maybe it's cause of stress over me not knowing, i also start to cramp when i stand for a long periods of time. i have also had vaginal cramping and when i went to the hospital on 12-3-07 they tested me for everything including std's and couldnt find anything. i wanted them to take my blood because if all else fails this would show pregnancy but they wouldn't take it. Now, i did go get tested at a clinic on the 26th of November and it came out negative and my cycle showed up that evening. it stayed for 4 days and the other 3 days i spotted one spot of light pink blood. since then the cramping continued and my breast still hurt. my cycle in october was from the 28th to the 3rd and the last time i had sex was the following week. no protection was used and we weren't planning anything of this nature. i am scared to go and get another test done because i don't want a negative result, yet and still i don't want to worry anymore. i know it is best to find out so i can take precautions and start prenatals, but i want to know from you all what this sounds like to you. Thanks!