@laurie123 yesssss meeeee! I find it is so hard to tell whether it is Tamoxifen, or normal stress etc but I know that since I started Tamoxifen in October last year my anxiety has gone through the roof and I do feel quite depressed I guess at times. You have described it perfectly feeling flat, I find some days I am just so flat and others I can be quite ok and then some others just no good at all.
I am actually just about to start some counselling as I think dealing with the "cut free" feeling after finishing treatment has not been easy for me and then factoring in how Tamoxifen is making me feel I just felt like it was time to offload.
There was a suggestion in a previous post of taking half a tablet morning and half at night which I haven't tried but I take mine at night regardless. It could be worth talking to your Onc about as they can change brands etc if it all gets too much.
Sounds like you are doing everything you can, exercising is great I find that helps too. I will be mentioning how I am feeling to my Onc next week when I see her to see what her suggestions are. It is miserable to think that something we have to take for so long makes us feel so lousy.
I wish I had pearls of wisdom for you, but maybe it will help just to know you are not alone :)