I've not had the surgery, and I'm sure some post wrap folks will be able to help...... However, meanwhile I wonder if it is to do with the fact that it is a dense protein? Perhaps you're just not able to break it down efficiently as yet, so it lingers and then causes discomfort. Have you stopped antacid medication now?
You could try some digestive enzymes next time you eat it, or try making meals with pork or turkey mince instead? Not sure if that would be great for lasagne but we use organic pork mince for chilli con carne (very mild kiddie friendly chilli!).
New stuff: GERD. Interstitial Cystitis
Lifelong stuff: Food allergies, eczema, asthma