My last period was on the 15th of February, and I was due on 16th of March so I was late, it took two weeks before very very faint positive, went for a scan and they wouldn’t see anything so they took my blood and my hcg was only three hundred, had more blood drawn today and it’s 650ish but I should be seven weeks so how come my levels are so low, miscarriage ? Ectopic pregnancy? Chemical pregnancy? Why are my levels so low for 7 weeks? Any ideas?

TIA