What Causes Irregular Periods After Removal Of Cyst From Breast?

hi I have had 8 cysts removed from my right breast and I have had 7 cysts removed from my left breast. that was in septermber I had another mammogram and ultra sound and I have new 7 in my left and not fibrostic tissue in my right. I have not got my period regular in 5 months. What do you think I should do they want to put me on tamixofen but I m scared of that drug and my doctor is worried also for that drug