From my experience if a doctor acts like that it is simply best to move on to another doctor.
I had a doctor who dd the same thing when I was having neurological lyme symptoms around two years ago when finally a different doctor suggested a lyme test. Imagine I had listened to this doctor saying everything is fine.
It's best to find a doctor that has some background in tropical medicine. They could possibly order some serology blood tests for certain parasites like Fasciola and others, as well as comprehensive blood tests to see what else is going on in the body.
I recently tested positive for protozoa but suprisingly fasciola came back negative but I've also seen flukes come out of me before so its possible I have another species if its not false negatives.
There are also options to get medicines for these through different sources but it can help if a doctor can be found that is willing to work and help diagnose and treat the condition.