Frustrated!

So I don't want to be one of those people who name off a bunch of pregnancy symptoms so it sounds like duh you are... But i am super gassy, have cramps, lower back hurts, my nipples are somewhat sensitive and I get dizzy whenever I get up a little sick after eating and I'm a week late on my AF. Thing is I have taken 3 hpt they are negitive and the one at my doctors (urine test) was negitive. We had sec the 20th of November and I had cramps in the middle of the night that night and on the 5,6,7,8 without a condom. Basically I feel pregnant and I don't know how none of them are coming out positive