Antigen testing is not really reliable. I am speaking from experience.
One thing might be worth considering. Even if they diagnose you, will they be able to treat you successfully? In my experience this usually does not happen. A few rounds of ivermectin is unfortunately not enough to get rid of this infection. Also, It might be that you have other underlying infection(s) and that is why your immune system is compromised. There are also other factors.
If you search for sharkman's previous posts, he has done a strongyloides protocol and it took him months or over a year to recover. He is still taking meds periodically to stay on maintenance and prevent himself getting sick again. He has done more meds and more intensively than just a few rounds of ivermectin. You should consider self treatment, as i suspect they are making this difficult as to make an excuse as they do not know how to treat such cases. All information is readily available on this forum.