What were your numbers? I have had a few losses, and that could be why I have always had lower beta numbers. This time my numbers are higher which could mean that I have one healthy really healthy baby or possibly two according to my doctor. At 14dpo I was at 316 and at 16 dpo I am at 807. I was hoping to compare my numbers to yours if you don't mind.
Thanks! 
Re: For those who had their betas done...
2 chem preg, 4 failed IUIs, 2 canc IVFs, 2 BFN IVFs, IVF #5 = BFP!!!
3/23 Beta #1 @ 17dpo = 913, Beta #2 @ 19dpo = 1724, Beta #3 @ 21 dpo = 3240
First u/s 3/29 @ 5 weeks 2 days - 3 sacs 6 weeks 3 days - 3 heartbeats 8 Weeks - Lost Baby C, Babies A and B going strong
My numbers are in my siggie too, congrats on the BFP
your beta numbers were low b/c you had m/c in the past... the low beta does cause the m/c (not sure if that is what you meant by 'that could be why" but wanted to clarify if it was).
my twin betas were almost the same as my singleton betas - they really mean nothing - but your betas are good and strong and that is what matters- so congrats!!
FYI, there's a good forum on this: https://community.thebump.com/cs/ks/forums/thread/7724217.aspx
Mine were:
320 (13dp3dt)
731 (15dp3dt)
1971 (17dp3dt)