I felt exactly as you do. I even started a thread about Feedback (whistling), because I was sure everyone had the same problems that I had, but I was so disheartened when I found out that I seemed to be in the minority. I have tried 2 different Siemens NHS aids that came out 2 years ago. Another from 3 years ago. A pair of CIC’s and I just trialed the Seimens Pure 700. Since the Pures would have cost about $5,000 - $6,000, I thought being a high end instrument, my problems would be solved. They were the worst when it came to feedback!
Various audiologists tried different domes and settings and nothing helped.
I am now trialing another pair of expensive Phonak Audeo YES’s. When they were in, I almost held my breath when I put my hands over my ears, getting ready for that awful shrill. BUT, I tried everything and…I could not make them make any noise whatsoever!!!
I think the biggest reason is because I have a custom mold. It is tiny and clear. The tube running from the aid to the mold is almost invisible too. I don’t know if this also helps, but the receiver is in the mold too which definitely improves the sound quality for me.
I do not live in the States, so someone else will be able to help here, but I think for customs molds you will have to pay around $60 (?). Also, I have read on this Forum that the best maker of molds seems to be Westone.
I hope this helps.