am i pregnant

my Friends (boys) think i am pregnant because my stomach look out. i been having cramps with no period and backache,sometimes a day in a week i will feel a need to trough up, heartburn, and i be feeling very sleepy but sometimes i cant go to sleep and my breast hurt if i slightly pinch them then on one of my breast i have a green unlikely to see vain in it.. i know i herd that you can not get period while your pregnant is it true or not. i haven't been feeling me lately.then the bottom below and around the navel feels hard but when i sit down it feels soft. when my stomach cramp bad and i go eliminate waste cause you know how you have to push it hurts. might sounds crazy but my period is regular and every since i had intercourse my period been out of wack. 6 days after i did it i slightly spotted when i wiped i wiped again and nothing came out.the day after my period came on which was 2 or 3 days late, then the next time it was a 55 days cycle which was not normal. then this month is it is 1 week early. if your period did come on the first three months while your where pregnant was it early.if i was to be pregnant i would be in my 3rd month and my urine and blood test was all negative which was tooken like the 1st or in the ist week in the 2nd month.