Weight gain 😫

I'm trying not to stress out but so far this pregnancy I have gained 25 pounds. This is my third pregnancy and every single one I gain roughly 40 to 50 pounds no matter what I do. I lose the weight after I have the baby but it's almost like my metabolism just shuts off completely when I'm pregnant. I just gain weight so easily when I'm pregnant. I haven't changed my eating habits I don't eat a lot and I don't eat terribley but at the same time I don't eat only fruits and veggies. I'm trying for a VBAC this time my doctor keeps telling me that I'm not gonna be able to if I keep gaining weight but I can't help it, I just gain weight so easily during my pregnancies. I gained the most weight with my first pregnancy when I was 19. I gained about 50 pounds and gave birth to a baby girl just under 7 pounds. No gestational diabetes either. My second pregnancy with my son I gained about 40 pounds and he was about 9 pounds. This one is another little boy and I'm so terrified that he's going to be big and I'll have to have a C-section.