When do side effects of anastrozole begin?

I was taking Anastrozole at night before bed. That's what was recommended. After about 7-10 days, I started with a slight ache in my teeth (or so I thought). I had been to the dentist for a cleaning with no other issues. So at first I thought the ache was that and used Tylenol to alleviate. But the pain kept building up stronger and longer over the next 2 weeks . Sometimes in my upper jaw, sometimes lower jar or both. It would come and go. But it built up to quite a point that I couldn't lay flat at night. Bearly slept for 3 nights in a lazyboy. Pain would build up and stay strong like 11 for a long period of time but eventually slack off and even be gone for a few hours. But it just kept returning and Tylenol was no longer helping. I was told to go off the Anastrozole and all the pain was gone within 24 hours with no reoccurrence. Now I've been prescribed Exemestane and just started it. However I'm terrified of what side effects this will bring.