I feel im the worst mom

Hi i just found out im 12 w pregnant. And sad to know that i have cyst size of 2.8cm outside my ovary. I know its not that worst yet, but to find out bout that i dont know how i can cope with being pregnant and handling 2 kids below 3. I even lose weight. Sometimes i dont know what to eat. And everything is on me. I feel sad that ppl say my 11 mnth baby quite light. I feel like i didnt do my job by giving my kids a proper meal. How to? I myself in this condition.