Yas, I've got a retroverted uterus as well and the sonographer was able to see bubs fine doing an external scan at 7 weeks. Of course, it depends on equipment and the preference of the sonographer... just thought I'd give you some hope that you won't necessarily have to have internals (or 'dildo-cam' as I have heard other girls on here refer to it!!!) for that long .

Good luck, hope you see something on Monday and that you get to see a lovely heart beat very very soon.