Mental Harrasment by Mother-in-Law

I have been married nearly 5 years now. It was a love marriage. This is my first marriage but my husband's second marriage. I went out against my parents to marry him and so the relation between my husband and my family is not normal. On top of that my mother in law keeps on harassing me on one pretext or another. She keeps on comparing me with the first wife (who had left home within a year's marriage) and also to other women my MIL was interested in getting her son married. I was a working woman and used to go to office before my husband did. My MIL kept on telling lies to my husband about me that I do not keep the house clean and do not do any work, whereas whenever I want to do anything, she will start heckling with me and not let me do anything. For some reason I had to leave my job and am at home and do most of the work, even then she keeps on lying and keeps on pointing fingers and very small mistakes of mine, which are very minuscule just to highlight it to my husband that I cannot maintain the house properly. She would get up early in the morning at 4:00a.m to complete all cooking and then keep on complaining that I do not do anything. She also has issues if I go to visit my parents and have verbally abused me and my husband also for that. Also whenever she sees that I & my husband and talking, laughing she starts complaining about me and orders me around as if I am her servant. All these years I have tried to be patient and calm, but I feel very much disturbed with her attitude. I have spoken to my husband many times. Though he understands, sympathises and loves me a lot, he told me directly (in a quarrel) that he will not leave his mother whatever might happen and if required he will divorce me. I feel depressed with all these and am spending sleepless nights. My health is deteriorating and I have to take sleeping pills now. I don't know what to do, as I love my husband a lot but I am not able to stay with MIL anymore. Please help.