Pregnant?

My boyfriend and I were having sex about 2-3 weeks ago and we were only using a condom (tried 3 other forms of contraception, none yet agree with my body). Once my boyfriend had cum, we noticed that the condom had come off completely. A couple of days later i went to take the morning after pill and I was told that it may not be 100% effective due to the amount of time. Ever since i'v been feeling sick,my nipples have changed shape ever so slightly,the sides of my boobs have become very tender ,had weird pains in my belly, dizzy, had spotting and eating tons more and not yet had my period. I have however taken a pregancy test and it said negative, but im wondering if i took it to early? Im getting quite worried now because im only 18, i'm probably just being paranoide but i cant just sit and wait for another sign. Any reply will be very much appriciated! Thanks x