really sorry for your loss - you sound like a wonderful couple who will be the best support for each other through this time.
i think you will need a referral for an OB, maybe call the GP and ask for one (you can usually tell them which OB you want, so perhaps call a few to see who can see you at short notice as they do get v v busy) or as the others have said you could go to another GP and just request the tests that you want (or back to yuor GP and explain you want to be v cautiousso could s/he order the following tests and take a list with you). You have a right to have the tests you need and you should def follow up.
Best of luck in the future and look after the 2 of you.