L.P.
It is safe to take thera flu!... And your milk will not go anywhere until it is ready something some parents do not know is as long as your baby gets at least that first two weeks of colostrum that is what is important. It may run out before you are ready for it to but it happens there is nothing you can do about it! It's okay. But it wont be because of your being sick! I breast fed all four of my children two of the four are twins! So trust me i know! I hope you feel better!
Blessings