My doc want me to take tamoxifen following lumpectomy for b cancer my FSH 28.5 LH 45.2 ostradiol 845 should I take it worried about side effects?

Likely yes. You are young and likely pre or peri-menopausal so tamoxifen is the drug for you, not one of the aromatase inhibitors. Tam has been in the market for several decades and in general is very safe. Odds of serious problems like uterine cancer or clots are low in younger woman. Discuss your concerns with your oncologist.
You should . Should follow your doctor(s) advise , benefits out weigh the few minor set backs . If you are not happy with advise take a second opinion your doctor will encourage it . Please do not stop the medication.