"Is Tamoxifen causing mood swings or am I just stressed?"

Probably both! I was definitely moody when I started taking it but a few weeks in it leveled

Have you had any other side effects

Joint pain, like I understand why older people always complain about stairs now. But I’m trying to just keep my body as active as I can which helps. Hot flashes, but I take mine at bedtime, so they come on in my sleep. Brain fog, dark thoughts, easily aggravated. It’s a little better now that I’m aware it’s hopefully just the tamoxifen and my cycle causing it. If it gets worse, I might ask about which anti anxiety and anti depression meds are ok on tamoxifen.

Many people taking Tamoxifen do report mood changes as a side effect, so what you're experiencing could definitely be related to the medication. Dealing with insurance and hospital frustrations on top of treatment can certainly add to stress levels too. It might be worth discussing these mood changes with your healthcare team to help determine what's contributing most and explore ways to manage it better.