MPN Advocacy and Education International has been trying, on behalf of Vietnam era vets, to get the VA to include MPNs on the presumptive list for years. The link to their advocacy page is here:
https://mpnadvocacy.com/blood-cancer-advocacy/
This may be of interest depending on your eventual diagnosis. Hope your doc gets on the stick with that.

Dad worked in the plant where they made Agent Orange and napalm. We both ended up with ET. Finding environmental causes for these cancers, however, is not high priority.

Best to you.