Hello, and welcome to Atkins.
I suffered two miscarriages in the past so I know how you feel. But there is no reason you should not go on to have healthy babies in future. Sometimes there is an obvious reason for the miscarriage; at other times, there isn't. I was told that sometimes the pregnancy does not 'take' properly, or whatever, and the body recognises that it could not have gone on successfully to full term, so it ends the process at an early stage. At other times the 'medical' reason is inconclusive or unknown. Either way it can be devastating.
Take some time to take care of YOU. Eat healthily and well, as we all do on Atkins. I am vegetarian and thankfully the most recent Atkins book (A New You) has plenty of info for us veggies. Eat tuna if you wish to of course but don't feel you have to.
Eating good healthy food makes us feel so much better. Starving, I think, all too often has the exact opposite effect. The brain is a muscle, the most important one we have, and it needs daily nourishment, just as the rest of the body does.
Welcome again to the Atkins board and feel free to ask away should you need help or advice. Be kind to yourself! Before you know it you will be strong and well-nourished and eager to try again.
Good luck hun!