Mine were low, but doubling (at first) for my c/p. Went from 16 to 35, then kept rising but the doubling time got slower and slower until it barely increased and we knew it was over. Never even got to 100 by 26dpo. Even if my betas had doubled appropriately, my chance of a viable pregnancy would have only been 30%.
Unfortunately, I don't think there is any possibility that yours is a viable pregnancy and I'm shocked that your nurse would give you hope. When the beta is as low as that, the doubling time should be much faster. If it went from 3 to 30, I'd say you had a chance. I'm so sorry :-( (((hugs)))