will i lose my rights to my children's if ever my husband filed me a divorced?

i am married to a British guy and we have 4 kids. we are married for 13 years but we just moved here in London for 3 years. my husband applied me a provisional visa and it will expired on feb. 2013. now i am under treatment of chemotherapy in breast cancer. and my husband want me to file a divorced and i don't have any benifits and i don't have my own bank account either. he i am worried because he always telling me that all our kids will live to him and he will send me back in the Philippines and he won't also renew my visa. and he is blaming that it's my fault why i have a breast cancer now... please help me what should i do? or what is my rights?