Hi Jane - nothing is too personal to discuss on here!! I'm 51 and had some spotting after I had been on Tamoxifen for a few months, and again recently. The doctors are quick to check out any bleeding while you are on Tamoxifen as it can cause changes to the womb and possibly womb cancer. To reassure you though - they are not so worried about bleeding in the first year, it is more so after that and you have only been on it for 3 months. That said, my advice to you from my experience would be to speak to your GP and he/she will probably refer you to a gynaecologist/clinic for a check or at least monitor you to see if it continues.
It's always hard to know what to do - please ask if I can help further. Wishing you all the best as you go forward.