Discharge? Or Spotting?

Ok so this is probably TMI. But earlier today I noticed a tiny spot of brownish/red on my underwear. I'm not supposed to start my period for another 5 days and I don't think I have a UTI or anything like that because I don't have any other symptoms.. My husband and I have been trying for about 2 months now so I thought it could maybe be implantation bleeding. So I took a pregnancy test and it was negative but when I wiped myself (I just thought to look) the toilet paper was that same brownish/pinkish color. Could the Prego test be wrong ??