@Claudia79,
I agree that this needs to be checked out with a doctor. However, I did read on here about another lady who developed a rash when she changed brands of Tamoxifen. She was reacting to one of the ingredients that was different in that particular brand. When she swapped back to her original brand the rash went away.
I am sorry I don't know which brand it was. There have been a number of women (myself included) who have had different or worse side effects from different brands of Tamoxifen. This might be something to consider and rule out in your situation. Deanne xxx