Cramping in the lower stomach and back

Hi all, I am very concerned. My husband and I have been trying for a few years and nothing has happened. well I lost quite a bit of weight and now I am experiencing all of the pregnancy symptoms. I am tired, and weepy, I have been bloated, and dealing with nausia for about a week. This weekend I noticed that I was bleeding only slightly, like when I wipe i see like reddish pink blood. I am not dripping and there is no blood in the toilet. I started cramping this afternoon, in my lower stomach and just above my tail bone in my back. I did alot of walking today around the MSU campus as we were at teh football game and I am concerned that if I am preggo I might be losing the baby. I hope that is not the case but I do have concerns. I took a test on Thursday and it was neg. My doctor had my blood drawn and she brought the preg. up after a pap so I am just confused... please help.