Could The Fluid In My Uterus Delaying My Embryo Transfer Be Caused By My Bilateral Salpingectomy?

I am waiting may schedule for my embryo transfer I undergone bilateral salphingectomy..everything on my ultrasound are normal and my doctor adviced me for my follow up check up if i will menstruate last november my menstruation occur that was my 1st mens after mysurgery, I went to my REI doctor but they find out that i have a fluid in my uterus causing my embryo transfer to postpone. my doctor cannot determine the cause where the fluid comes from But instead she gave me a progynova and dupasthon..I just to ask if what causes the fluid in my uterus..is it due to my operation?