I can vouch for this toothpaste (it's called Repair & Protect). After about a week of use, no more pain when eating or drinking cold things. It had gotten so bad that I could hardly swirl even lukewarm water (do see a dentist too though if you have problems).

There are independent studies confirming the efficacy. The active ingredient binds to dentite and forms a protective layer, which lasts about a day.

It's OTC in Europe but afaik on prescription in the US. Maybe buy it from an EU web shop, it's no more expensive than a regular toothpaste.

There's a similar formula available in the US called Biomin that's FDA approved and distributed by Dr Collins. Their fluoridated version isn't FDA approved yet, but it works well for me used 50/50 with an OTC stannous fluoride toothpaste.