Twice now I've tried pan frying fillets of white fish (Swai and Flouder) in olive oil and butter.  Both times the fish has disintegrated into unsightly mush.  Is there some technique I'm missing?  How can I pan fry without the fish falling apart? 
When we pan fry white fish, we use a non-stick but do not marinade nor bread it.   We stick a little bit of oil in the non-stick; just enough to cover the bottom. Heat the pan up until the oil is shimmering and you can smell the oil (for example you will smell corn for vegetable oil). How high of heat really depends on your burner. We have a gas stove top and use the large burner at 5 1/2 and our non stick is an all-clad stainless steel (no copper). Put your fish in the pan and do not move it for a few minutes. You should hear sizzling but not crackling. If the fish in the oil is crackling, turn the heat down a little. At the end of a few minutes, shake the pan and see if the fish slides around. If it does not, the fish may need a little more time on that side. To help it along my husband likes to shake the pan every 10-20 seconds to get air pockets under the fish and allow the oil to coat the bottom of the fish some more. Once the fish slides, flip it and remember how long you cooked the first side for just to have an idea. You will cook the other side for less time. Watch the sides of the fish to see how the cooking progression is going. If you want fully cooked fish wait for the sides of the fish to almost become fully opaque. Think of when you are watching even thickness chicken cooking from pink to white. Resting time under foil will cook the fish the rest of the way.   Tips   If the filets are not even thickness, move the thinner ends to the cooler sides of the pan. You can also fold over the thinner side (more common with salmon filets) to match the thicker part and stick a tooth pick in it, that way the filet is the same thickness all the way around. If you have a sauce to pour over the fish, make the sauce while the fish is resting. This way you are able to cook the fish on both sides to get a nice crust without worrying about the sauce steaming the fish. If marinading the fish, take the fish out of the marinade and let drip for a few seconds to get enough of the liquid off then follow the above tip to make a pouring sauce. For skin on fish, we usually put the fish in skin side up first then flip it  