False Negatives?

Brittney • 23, married, TTC
So my husband and I have been trying to get pregnant off and on since Christmas (had to stop when he deployed and I was going to deploy but didn't) anyway, in January I was almost certain I was pregnant until a blood test said no after being 3 weeks late on my period. they said it must have just been "stressed". But now we have been trying again and my breasts are sore, cramping (I never get cramps), I'm constantly tired, grumpy, and nauseous. My husband told me not to get excited just yet because of how "sure I was" last time. But today I started spotting and my period doesn't start for another week. 
I also never spot before my period... But I took a pregnancy test this morning and it said negative. I just don't want to get my hopes up... Is it possible that it's a false negative? Anyone else have a similar experience? It's so hard to tell if it's just a bad PMS experience or if I'm pregnant...