Bleeding...

Found out I was pregnant last week. I was spotting after sex (Wednesday-Sunday) and went to my MW on Friday. HCG was 12. Monday HCG was 74. Wednesday is was 152. Ultrasound on Wednesday showed nothing. I was assured that was normal and I am probably just really early. I didn't have a period in September so I have NO clue how far along I am. Today I am spotting again (fresh blood) and crampy. Took a test hoping it would make me relax but didn't work! Any ladies with experience? This would be baby #4 for me but I never bled with any of my kiddos. Kinda freakin out!