What Are The Early Signs Of Pregnancy?

Today I took a home pregnancy test (e.p.t) because i am four days late. The result was negative. But I do not remember my period being this late before,although my periods are never regular. I use to start around the 5th of each month and now for about a year i have been starting on the 28th of each month. I am not having any symptoms, my last period was the 28th of september. then i had sexual intercorse around october 12 or 15th, we did use a condom but before he put the condom on we messed around for a couple of minutes but he did not come before we messed around or inside of me at all. after maybe about three to five minutes we put a condom on and continued. so i was wondering if the pregnancy test should be pretty acurate or would it be to soon? and also i have been taking b12 vitamins,now would be the third month taking them,could they make me late on my period? i was slightly anemic that is why i had to start taking the shots. Thank you so much for your help.