Anybody else test negative but still end up pregnant?

I'm in a different situation because I still breastfeed my 13 month old and have yet to get my cycle back. We've been trying and I suspect I did ovulate, but I have no idea where I am in my cycle... Basically I've been having cramps for 4 days, but I keep getting negative tests. If this was my period I feel like it would have shown by now with all the cramping... I'm going absolutely crazy because I'm convinced I'm pregnant but these test keep saying otherwise.. Could it be too early? Am I just crazy? Lolll