My husband had this problem. He lost 100 lbs in high school and for more than a decade afterward lived in terror that he would be fat again. Like you, he was about 130lbs at 5'10," which was waaaay too little and not attractive either. Because he was starving himself (not nearly as much as you are, but keeping himself under 2000 cals a day for years when he really needed 2400) my husband ended up with severe mental and emotional health problems that could have lead to his death and would have eventually lead to divorce because I ended up the target of the negative feelings that kept raging out after so much starvation. (He was also weak and sometimes I would have to carry things when he couldn't). Eventually we got him to a counselor who helped hm gain self esteem and helped convince him to eat an amount that was healthy for a 35 year old, 5'10" man. He still meticulously counts his calories in a way that can be obsessive, but I'm just grateful that he now eats enough and is up to 150 lbs. Oh, and his abs look better too- they are stronger and not surrounded by protruding bones. His mental and emotional health are restored and I am now married to a sane and (mostly!) peaceful, healthy man. I don't want you to end with the same problems my husband had. If you feel that you "can't help" but eat only 340 to 780 calories a day, please get some professional counseling right away to help you get enough self-esteem to put your health above your abs. And you know what? You don't have to choose- you can have health AND sexy abs. But starving yourself will lead to you not having either, because such a low calorie diet will slow your metabolism, and as the above person pointed out, eventually cause your body to eat those muscles for fuel. I'm saying a prayer that you find the help you need!!
"Whether you think you can, or you think you can't, you're right." --Henry Ford