Feeling very upset and like I'm failing

I have been nursing my son since day one and loving it. I wouldn't have it any other way. He is now 7 weeks old. My fiancées family is total formula junkies and have been trying to push it from the beginning. Every single thing that goes wrong or if he is fussy, they automatically go to "why don't you try formula". I finally got them almost over that and now I find out that in 5 weeks I am having major surgery and really don't know how nursing will be. I will have to hospitalized for 5 days in a hospital an hour away and then 6 weeks no weight bearing, basically bed rest. And on top of that I am sick and my antibiotics made my supply tank yesterday. ( infront of my formula junkie mother in law)