It wont do you any harm if you take milk thistle with it so go for it!, takin nolva througout a cycle to prevent a condition that you may not be susceptable to is just a waste of time, the rule of thumb is to have it on hand just incase you need it!, and if you dont need it this time then you have saved your nolva and spared putting and extra compound though your body unnecessaryly.
When your nipples become sensitive (Tender) and puffy start on the nolva and the syptoms will go away when its has bound to the receptors sites in around 3-4 days maybe sooner, the lumps dont form for about two weeks after feeling the first signs of sorenes so there is plenty of time to act and administer the nolva.
having tits isnt that bad...They give you somthing to play with
Just relax and enjoy your cycle.