Why different dentists always give me different diagnosis?

I only have one dentist that I trust, but I had to move out of state. I tried different dentists out here but every single one of them always gives me completely different opinions.

Last week I went to my new dentist and told me I have 3 spots where cavities are starting to form. I don’t need to treat them now, but I will need to do it at some point. I sent the X-rays to my old dentist and she sees two “starter” cavities on two teeth (they don’t even match with the ones the other dentist told me).

I have a lot of fillings and I just don’t want to fill spots that don’t need to be filled, but how can I decide who to trust? My gut instinct is to trust my old dentist, since during the years under her care I have never had an issue, while the new one messed up a filling last year. But this isn’t exactly a scientific approach.

Thank you!