Anti d

I went to my 28 app they took my blood then gave me the anti d injection. They rang me 2 days later, my blood had been rejected from lab. Can I give another sample, which I did. They then ring me back again the blood sample I gave is showing up as having anti D in it so they need to take another sample and send it to another lab. So I told the midwife off course its going show up up with anti d In it because you gave me the injection after the first lot of blood was taken.

anyways ive been reading online if your body has already started to produce the antibodies the anti d injection would not work. therefore im worried the lab is not going be able to tell if the anti d injection will work because they cannot see my blood had any pre-existing antibodies before the anti d injection!??

anyone got any comments/thoughts