Anxious

I thought I was further along then I apparently am. Due to my super irregular periods I am only about 5 weeks along. The doctor wants to see me again in two weeks to hopefully hear the heartbeat. He was not able to pick it up at my first appointment. Has anybody else experienced having to wait to make sure everything is okay? He said aside from not being able to pick up a heartbeat just yet, everything else looks great. How do I not stress about the unknown?