anna_paola - I am so sorry to hear things haven't gone well. The practice of doctors waiting another week to do a follow-up ultrasound is largely to protect themselves on the off-chance something develops. In some cases, the embryo IS developing slowly, and does appear late. However, considering your low and very slow rising betas, there is little doubt this is a blighted ovum. 34DPO is close to 6w pregnant, depending on what day you transferred, and there should clearly be a fetal pole and sac, if not a heartbeat. At the point your hCG reaches 5000, there should be a visible sac and the beginning of a fetus at the very least. Since your sac was empty, it will very like not develop into anything further. Again, I am so sorry.
Blighted ovum pregnancies are often due to chromosomal issues where the embryo implants, and begins to develop, but then stops. Some occur earlier than others. My guess at this point is that you will just miscarry this on your own a few days or so after you stop your progesterone and that you will not need any further intervention. I've experienced MANY miscarriages, and usually, at this point, I would go ahead and stop my meds so I am not delaying the inevitable. However, if you chose to stay on your meds, just to be safe, I wouldn't blame you at all. You will likely continue to spot and maybe bleed lightly, but continuing progesterone will probably prevent the m/c from fully taking place (or, your body may begin the process in spite of it).
My thought would be to continue your progesterone and then see if they will do another hCG level for you in a couple days. If the number has decreased, or hasn't risen, you'll know for sure. Otherwise, you can wait until next week. Chances are they will not do an u/s earlier than a week as they need to give things time to actually change, and 3 or 4 days isn't usually enough time.
Good luck to you.