How far postpartum are you I'd wonder too, with regards to the ab eosinophil count. Because autoimmunity post-pregnancy is a thing. I just happened to recall the other day.
epidemiological examination that was done due to the known prevalence of AID happenings during and postpartum:
Pregnancy and the risk of autoimmune disease: An exploration
findings of immune related happenings (curing of rheumatic arthritis for example by pregnancy) while other AID remains the same, or development of new AID:
AUTOIMMUNE DISEASE DURING PREGNANCY AND THE MICROCHIMERISM LEGACY OF PREGNANCY
Easier non-science reading if you just want the concept without the science behind it:
Having a Baby Makes Mom's Body Turn on Itself
It happens. There is a correlation. Its nothing to freak out about. The whole cancer thing you are stuck on likely needs to be rolled up and thrown right in the garbage for now as far as worry goes.
I'm leaning heavily towards stress + postpartum AID.
Postpartum AID is very normal in many ways so you can likely stop sweating the eosinophils until you have a whole lot more diagnostics. Continue with the medical process and just get a calorie count in the meantime so you know if its truly unexplained weight loss or stress induced. Eat the same stuff every day if necessary.