No AF but still having BFN's!

So I've been off BC for about 5 months and hubby and I have been TTC. Even with no BC I'm completely regular, 28 days every cycle so this month is seriously off! 3 days late (should have started Tuesday 2/12) and no sign of AF and I usually have heavy cramping starting a day or two before but not even a hint of that. Mild nausea and serious cravings, slightly sore boobs but a negative home test and a negative Drs test. Had blood drawn today but those results won't be back until Tuesday 2/18 at the earliest. I was treated for a URI 2 weeks ago with a steroid shot and a rosepherine shot...could this affect AF's arrival or could I really be preggo and it just not show up yet?? Help!!