5 weeks and 5 days

Hello! I took 3 pregnancy test na 2 magkaibang brand it came out positive then the next day pumunta akong ob para magpaultrasound pero sabi sakin is wala pa daw fetus na makita. Possible po ba yun? Nagwoworry ako... Then nagtry ulit akong magpt kaninang morning with different brand, it came out positive and malinaw sya... Natatakot lang talaga ako na bakit walang makitang fetus... ?