@kezmusc
I have to agree with the comment @melclarity "As wouldn't it interfere with its consistency? And effectiveness?"
If you are having that much trouble then perhaps you need to insist on being put on a different medication and/or ask for a referral to a Dietitian and Exercise Physiologist so that you can work your intake to work best for you to trigger your metabolism, improve your well being, without spending monies on pills that may not be as effective.
As to Letrozole, and or Tamoxifen for that matter, I don't know how long we have to take them before the side effects are defined as being from the medication. As noted in a comment earlier the weather plays havoc for some with joint pain and if you are starting from a low base with bone density, cholesterol, fitness et cetera no doubt that all plays into effect on self!
I have changed to Letrozole as I had Tamoxifen induced gynaecology problems. I have been taking Letrozole for 35 days now and the side effects are the aching bones, joint pain, (which I had on Tamoxifen) but that doesn't necessarily mean that is how it will affect you or others as we all metabolise foods and meds uniquely. I have a good base for cholesterol and bone density but my fitness is at the lowest it has been for a very long time and I am in the process of improving that.
I hope you don't see this as a lecture as that isn't the intent; just hoping that you can think about how to work Tamoxifen into your every day.
I do hope you can find the happy medium where your body adjusts and you settle into routine.
Take care