Ceejelz, it's possible (according to urban legend) but very rare. However, when "heavily pregnant" you are very likely to get a BFN on a HPT, so that part may well be true! It's common for hpt lines to get lighter once you get past about 7wks and the further along you are the more chance you'll get a false BFN. Google the "hook effect".

Krikkit, FX for you! (For the list, just to confirm, do you mean tomorrow? The structure of your sentence made the tense (ie past or future) ambiguous.)