How long does it take ....?

I just lost a baby almost 2 months ago ... and I think I am pregnant again. I feel all the same symptoms tender swollen breasts ... back aches ... cramping ... head aches even the gas lol. ... I took a pregnancy test last night and it was negative ... but im just wondering how many dys or weeks do you have to be pregnant before the hcg will show up on the test. ??????