hey there, assuming the ultrasound was done vaginally, they should have been able to see a yolk sac at least, although it is not completely uncommon for it to appear a little later. There may be a chance that the pregnancy is not developing properly and you might miscarry but don't go banking on it yet, like i said its not uncommon for it to show up a little later. Also the no free fluid in the pouch of douglas, is a term they use when looking into ectopic pregnancy and rupture of vessels etc. it is a good sign if there is no free fluid. I hope all goes well for you lass, good luck and all the best :) I hope this helps :)
Are you certain of the 5w5d figure? If you ovulated later than usual in your cycle, could you be possibly only 4 weeks 4 days pregnant? At that stage, it would be too early to see much.