AF late, brown spotting and cramps...

I normally have a spot on cycle, I gave myself a break this month so no bbt or OPKs so I'm not 100% sure when / if I ovulated... AF is now 3 days late but I have occasionally brown spotting when I wipe... Very light - not enough to show on a liner or underwear. I have quite pronounced cramping on my left side, feel nauseas, am exhausted and have sore boobs - the normal AF symptoms! I *think* I'm around 13-14 dpo... My question is, has anybody been in a Similar situation and been pregnant? I tested BFN this morning btw... Any feedback is really appreciated!!