R.L.
Your OB's office should have a nursae omn call that you can ask. I would suggest this if you are feeling really awful.
I think thera flu has pseudophedrine in it, if so that is not safe to take while nursing or pregnant. Regular tylenol should be OK to help any aches, but as someone else suggested you should check and see if you should be nursing while sick. (I've never been told not to, but it wouldn't hurt to ask.) You could also check with the pharmacisit but they don't always know and if you have other health questions you definitely want to ask a nurse so call your doctors office they should have an after hours number or an answering service for this types of issues!
Hope you feel better!