Newton,
I know it may seem stupid, and counter-intuitive, but there’s a possibility you are not consuming enough calories, and that by eating slightly more, you would actually lose weight quicker.
My own experience is that if I reduce my food intake too drastically, my body seems to think my throat has been cut, that lean times are ahead, and that it has to do everything it can to preserve the fat stores. So this means I feel knackered all the time, I’m likely to exercise less effectively, and just generally feel flat and lethargic... However, if eat just a little bit less than normal, and maybe increase how much I burn through exercise, this works much better (and I feel a thousand times more energetic)....
I‘m not a doctor, and may be talking nonsense, but as a big(ger) bloke, 1200-1500 calories a day seems too low for me. It may be worth experimenting with upping your average calories to be more like 1750, and just making sure you are doing a bit more walking / other exercise (only to a level that gets your heart rate elevated and a light sweat)...