5 weeks 4 days pregnant and spotting

Tia • Been with my hubby for just over 6 years. Married on 10/11/13. Prego with babe # 1!!!
Hi all. So last night I was 5 weeks as 3 days pregnant. Went pee, and when I wiped I saw blood. Not bright red, but a pinkish color. I called the nurse hotline and they said if I start cramping bad or soaking a pad every hour to go to the ER. It happened a little the second time I peed before bed. Then went away. This morning they had me go in for my first US due to the spotting. They said its too early to see a heartbeat but saw the yolk sac. They said everything looked ok and couldn't give me an answer as to why I spotted. All day today I had nothing until 20 minute ago, went pee, and more light pink appeared on the toilet paper. Has anyone else experienced this? I'm so freaked out and hate not knowing what's going on. I last had intercourse on Sunday so it's not from that...