Get your thyroid levels checked... unless you're eating copious amounts of food and doing absolutely nothing for exercise there is no reason to gain that much weight on a weekly basis... It's very important...
Get Free T3, Free T4 and TSH.. Also get checked for Hashimoto's...
im putting on 3kg per week I'm 12 nearly 13 stone and got so many folds of fat that I can't count
I agree that you should get your thyroid levels tested... Hypothyroidism is often a cause of sudden, unexplained weight gain. Be sure you get a full thyroid panel, that includes Free T3 and Free T4, along with TSH; don't settle for just that TSH that many doctors will do and tell you is sufficient.
Also ask for thyroid antibodies to determine if you have Hashimoto's, which is the number 1 cause of hypothyroidism in the developed world. The tests you need for that are Thyroid Peroxidase Antibodies (TPOab) and Thyroglobulin Antibodies (TgAb)... Be sure to get them both, or you could be misdiagnosed.
You might also ask to get tested for Type II diabetes or insulin resistance/metabolic syndrome, which is another cause of weight gain/inability to lose.
maybe have your doctor check you out for hormone imbalances? sometimes thyroid issues cause weight gain.