Leesa your blood results if quantitive will give a rough idea of DPO - but an ultrasound prior to 12 weeks is the most accurate way of dating a pregnancy of unknown gestation. It sounds like it's important to know roughly how pregnant you are - though going by the inability of the 50miu test to diagnose the pregnabncy it sounds likje you are very early.

Give the surgery a call & tell the receptionist you have a path form for confirmation of pregnancy but tell her you specifically want to know what your levels are. Ask that they re write the form and fax it to the pathology collection centre you plan to attend. This is no great drama - or alternatively ask that they contact the collection centre to give permission for a quantitive test.

Good luck my love.