I had this problem years before surgery. I had 4 10+ pound children which started me with problems with constipation. The only thing that works for me is Miralax.
my dr. told me to take 2 capfuls every morning until I started to go and then cut it down to 1 cap every morning. I was doing great until a week or so after surgery
(who would guess you can get constipated just drinking fluids, but you can). Any way, used MOM until I saw my dr. 3 weeks post-op. he said I could start the Miralax again. What a relief, I go everyday atleast once, but you do have to drink atleast 64 ounces of fluid everyday or you can get dehydrated very easy on Miralax.