Hi Ryn, I drove from Melbourne to Gold Coast when I was 38 wks pg and then flew back later that night.
We drove from Melbourne to Coffs Harbour which was about 15 hours and stayed the night and then straight to the Gold Coast and I was fine.
I had warned everyone I would need to stop a few times for the toilet and to stretch my legs and I just relaxed and read a book and enjoyed the scenery.
Just make sure you have a mobile phone,plenty of fluids,something to eat,stop when you have to and I am sure you will be fine.
Have a good trip
Take Care
Michelle