Yes, I'm on Mounjaro - but also on empagliflozin and both long-acting and short-acting insulin, so my experience is some way away from yours.
I did find that 2.5mg of Mounjaro had no effect, 5mg had some effect, and 7.5mg shut down my appetite totally, so I'm back on 5mg. Of course "your kilometerage may vary", since everyone is different. (In passing, in the limited time I was on/able to get Victoza, I found it didn't have any noticeable effect on me at all...)
My only suggestion would be to hang in there, and see what effect the 5mg dose of Mounjaro has, Are you "under the doctor" or perhaps your local hospital's Diabetes Centre? "Lactates" have never been mentioned to me in the 31 years since I was first diagnosed, and I was on 3g of metformin a day for very many years, until it became contra-indicated for causing kidney function problems.