4 days late but no pos. test?

[Erinne]

I'm starting to obsess a little. I should have started AF Monday and I was having my usual PMS symptoms (moody, sensitive "down there," back hurts), but now I'm feeling better and it still hasn't showed. We were doing kinda lazy NFP and it's fine either way, but I'm just terrible at being patient and waiting to see. So what seems more likely, that I'm pregnant and the tests just aren't picking it up yet (cheapo dollar store tests) or that I'm just really late for some weird reason? My cycles have gotten a bit shorter since dd was born, but I'm still usually pretty regular. I'm going crazy!