That's the best reference I can find on a quick Google search, it even has images in case you wonder. I'm fine with toothpastes because I rinse thoroughly after brushing, but mouthwash needs no rinsing to be effective and after a week or so of regular use the inside of my mouth gets very irritated and sore.
Saying "mouthwash" in general is not specific enough. There are lots of types of mouthwash. I personally always go for flouride and alcohol mouthwash, so it kills germs and provides protection for my teeth. If the alcohol is what's hurting your mouth, use alcohol free anti-cavity (flouride) mouthwash. Maybe you're using the gingivitis mouthwash? Or the alcohol mouthwash? It doesn't make sense to say all mouthwash does the same thing to your mouth
Not yet, that might be something to ask next time I go to the dentist. Admittedly I didn't search exhaustively, I gave up seeing every mouthwash in australian supermarkets have it.
Look at the sensitive ones, often the cheaper ones don't have SLS in them. They're better but with some I still get issues if I don't rinse at all. For reference, Aldi sells one around here without SLS and with fluoride.