Hay, nakakaworry talaga yan, especially pag nasa work ka pa! I haven't personally experienced it at 13 weeks, but a few of my mum friends had light spotting around that time and honestly, kailangan mo talaga ma-check agad ng doctor kasi iba-iba ang reasons and kailangan nila malaman ang situation mo specifically, some were told to rest, iba naman normal lang based sa ultrasound. Wag mo palampasin yung check-up kahit busy sa work, mas importante yang peace of mind mo at ng baby mo. Rooting for you!