Momsh, I know this is stressful, 37 days delayed is definitely unusual para sa'yo! Pero honestly, with irregular spotting like that and a negative PT last week, kailangan mo talaga makita ng doctor para sure na, okay lang ang lahat. Could be marami pang reasons, pero hindi dapat mag-guess lang tayo dito.
Go see your OB soon, ha? Better safe than sorry, especially pag ganito ka-unusual ang cycle mo.