what kind of flouride are you using? If it is the older style stannis flouride gel, it is really hard on your gums. It has to stay on for so long, that it really starts to burn.

My oral surgeon (also my cousin) switched me from 10 minutes a day with trays and stannis flouride gel to one minute Oral B flouride foam.

Instead of trays, I would simply put a "blob" of foam in my mouth, move it around my teeth with my tongue, and expel it after a minute or so.

It was way easier on my gums, and less of a hassle. I still use the foam, now about half the time with trays and half the time without.

I'm a year out, and I have no problems with cavities at all. I think this approach worked well, for me anyway
Wayne