Advice needed ... Tamoxifen or AI?

[LizzElliot]

Hello ladies,
May I get advice. I have been on Tamoxifen for about 10 weeks and have gained 15 pounds. I did not gain weight in chemotherapy. My diet is mostly raw vegetable salads, often with some form of protein or seeds. Yet, the weight kept creeping up, so two weeks ago, I joined a gym. Working out for at least 30 minutes but usually 1 hour or more every day has still shown no weight loss, but weight gain.
Last week while in for Herceptin I asked to be tested for menopause status. (My onc had said at one year's time since the start of chemo, if I did not get my cycle back, I'd be considered post-menopausal, and presumably then switched to an AI.) So in April, if my cycle does not return, I would be considered post-menopausal, but at this weight gain rate, I wanted the test and the results show post-menopause.
So oncologist has approved starting Femara and quitting the Tamoxifen.
Yet, I'm reading here that many of you tried Femara and went back to Tamoxifen. Yet it seems many of you are post-menopausal. I thought we all switch to an AI after menopause. Is that not true, or does Tamoxifen work on pre- and post-?
I'm not sure why my doc choose Femara, but given the choice, would you recommend one over the other in the family of Femara, Arimidex and Aromisin?
I'm told there will most likely be side-effects to the AI, but my thought is to go through that transition before I start a new job. So that's my hurry. Plus I am hoping the new side effects are not weight gain.
I have not taken Tamoxifen for two days now and have seen a one pound loss each day.
I have Hashimoto's (hypothyroid), but a recent test shows that my TSH is very, very low and my T4 Rx has actually been reduced to get me back in range.
Due to all this, I can only think that Tamoxifen caused the weight gain.
I've been told people can gain 10 pounds but then it levels out. Since I've gained 15# and still gaining despite a very conservative diet and a fairly rigorous work out schedule, it seems I am not "stopping at 10 pounds" nor "leveling out".
Any similar experiences or advice or warnings would be so welcome!
-Thank you!!!!