not able to lose weight, doctors say its stress???

totally baffled about lack of weight loss despite sticking to slimming world, weight watchers and counting 1200-1400 calories plus daily brisk walking, cross trainer and lost next to nothing .. perhaps 4 lbs tops in 2 mths :(
im 15st11 lbs so should be finding it easy to shed the lbs its so disheartening, have big wedding to go to in aug was hoping to lose couple stone but not looking hopeful
I am under a lot of stress atm and do suffer from anxiety doctor said this is why not able to lose .. wondered if anyone been in same position and managed to kick start the losses again, its really getting me down and affecting my relationship :(