I lost my first 70 pounds in the span of 5 of months, which is 22 weeks. It averaged out to about 3 pounds a week. When you have a higher starting weight, it comes off alot quicker when you first start, and then slows down
During that time, I was eating a good amount, but didn't count calories. I stayed active during that period which may have played a good part in the pounds dropping at that rate...
Anyways...Personally, I wouldn't set a time goal like that for youself. Just lose and do your best, and whatever comes off comes off
Come up with a safe plan to follow. Excerise. Your body will lose weight at the rate its suppost too