Tamoxifen side effects?

Hi Ladies,  I am a 64 year old women had breast cancer in the right breast removed April 2012 it was small. I had 16 treatments of radiation.  Started Genox a brand of tamoxifin  in September I am having side effects, legs and  ankles swell.  Cramps in the legs and feet when in bed, Light headed when I bend down or sit up in the morning for sleeping. I also have large lumps in my breast with pain.   I have just starting spotting felt  frightened as was  I was told if you start bleeding it could be the start of cancer of the uterus.

So I am thinking of stopping the meds.  I feel unsure what to do it is a catch 22,  I would love to know if anyone stopped tamoxifin.  I don't want to take any meds. I haven't  taken any for three days and feel great but, am I doing the right thing.  I spoke to the oncologest on the phone he said it is up to me !HELP!.