Tamoxifen side effects?

Hi This is my first time writing - just signed up this morning. I was diagnosed with early stage breast cancer in December 2013. I've just completed 7 weeks of radiation and have started taking Tamoxifen. I've had a Mirena IUD for the last 8 years to help with terrible pain caused by endometriosis which has been great. Sadly, that has to come out this Friday on recommendation from my Oncologist. I'm 53 years old and not really sure where I would be at naturally with menopause given the IUD has masked symptoms. I'm wondering how soon after starting Tamoxifen I might experience any side effects? I'm hoping I am one of the lucky ones!! I've only been taking it for four days and already I feel anxious - the kind of anxiety that sits in your chest and makes you feel sick. Wondering if this is just general anxiety from the whole ordeal or if it could be related to the drug??? Not due to see my Oncologist for another six weeks.