when you first start Atkins most people usually lose a lot of weight the first few weeks. most is water weight due to your body adjusting to the new healthy food & lifestyle.
if you think your calories are too low try adding more fat...butter, olive oil, coconut oil, avocado. your body needs fat, just give it the good kind.
there are differing opinions on the minimum amount of calories needed, but I'll offer 1200 as a general guide. 1500-1800 is a good range to shoot for, but don't stress if you don't get it exact or make yourself eat if you aren't hungry.
i usually have a few low days & high days...i might eat a lot one day and not as much the next. do it more on how you feel.
I lost about 30 lbs on Atkins then converted to more of a Paleo way of eating