Hi Charlene, and welcome to our forum.
I see your main problem by looking at your profile - you haven't read any books.
You see, when you say you are doing "Atkins", I suspect you are doing something of your own devising. For example, peanut butter is definitely not permitted in the first 2 weeks.
It also sounds as though you are thinking of low carbing as "a diet", whereas it really has to become the way you eat forevermore.
And I wouldn't be so desperate to lose that stone. If you follow the plan (after reading the book of the plan of your choice - it doesn't have to be Atkins), the pounds will fall off in their own good time.
And if you are following the plan, you should not have low immunity. Atkins, and most other low carb plans, include lots of vegies along with fresh meat, fish (can be canned tuna or salmon), cheese and eggs - also low in cost.
All the best to you, matey.