What you are describing is once you hit $1500 of out of pocket medical expenses, you can get 20 cents in the dollar. It doesn't make any difference if Medicare or PHI have paid a portion, it's any out of pocket health expenses.
At the end of financial year, request Tax statement of benefits from your PHI and also Medicare and they will have any claims you have put in and show your out of pocket expenses and the amount they contributed.
So keep every receipt, especially the ones for the sperm as you probably can't claim any of that?, inlcuding Pharmacy scripts, again you can go to your Pharmacy and request a Tax statement of your or partner.
Last year I think they were claimed against my DH?
The ATO website has a very detailed summary of what you can claim. We always have our Tax done by and agent (DH's brother), he works out who it is best offset against usually.

HTH

ETA: I just googled ATO medical expenses and it brought up exacty what you need in the first search item.