Sorry to hear that @Zan .... When do you see your Onc next? Can you make an appointment as soon as you can & discuss switching meds - tho Exemestane and Letrozole are known to cause aches & pains too. :( Tamoxifen is the only one that I haven't tried yet .....
.... Also ask for a bone scan to make sure you're not losing bone density too & just overall 'checking' on your bone status ... I got checked last year when I had continual hip pain & got the all clear.
Take care & I hope you can get some relief xx