prometruim pregnancy and testing

Hi Dr.Q, I go for a pregnancy test on Friday, however that will be 12dpo so i am wondering if i could get a false neg. just incase i implant late? I am on prometruim as well and the only symptoms i have are dizzy and tired and some cramping, so this could mask any pregnancy symptoms. what i am asking is there is know way to know until pregnancy test b/c of prometruim? sorry so long. One more thing in my 1st preg. i didnt show up on any blood or urine test until i missed 2 periods, and the last one i had 10iu/ml 4days before missed period. i lost both hence prometruim prescription. could this test show late as well? thanks so much for your time.