Slowly rising HCG...

So I got the results from my 2nd beta and the doctor is concerned this pregnancy may be ectopic. My beta on 14dpiui was 104 and on 18dpiui it was only 235. That's only a 50% increase over 48 hours. The doctors like to see 60% at least for a viable pregnancy. I'm terrified...I go back in for another beta tomorrow but I just wanted to know if anyone here has gone through the same thing where your numbers started out slow but picked up later on...holding on to hope but I'm so nervous.