Threatened Miscarriage/Ectopic. Low HCG

Mistica
Hey Guys! Looking for someone who has ever experienced something like this. This is my 5th pregnancy, and I have one live birth. All of my miscarriages have been in the first trimester, prior to 9 weeks. This time, I know exactly what my dating is like because my husband was working away from home and we only BD one time. I should be 5 weeks 4 days. My HCG has been low and slow rise. My betas are drawn often because of my high risk of recurrent loss. I got a positive HPT at around 10 DPO and then the following day, Dec 23, I began 3 days of heavy bleeding. I thought it was a chemical pregnancy, so I went in for more bloodwork to verify. I was found to be still pregnant with low HCG, although it was rising quickly with good doubling times. It's been a roller coaster with low HCG and now it's going up and down. 
HCG Timeline
12/26-Hospital Lab: 20
12/28-Quest: 45.8 (29hr DT)
12/30-Hospital: 157 (27hr DT)
1/2-Quest: 124 (decline)
1/4-Quest: 130.2 (681hr DT)
My doctor is now starting to become stumped, and wondering if I am having an ectopic pregnancy. My HCG is too low to show anything on ultrasound, and I had one last week. I will be having another scan tomorrow, and then talking about management. I believe they will want me to do a few more HCG draws too. Has anyone ever had betas like this? I feel so alone because they are so strange.