To be absolutely honest, considering that you have an eating disorder, that your current BMI is in the healthy range and that your goal BMI is not within the healthy range and would make you underweight, I would recommend 2 things.
Firstly, have a good think about it. Do you really think that you need to lose weight? Or is that your eating disorder talking? Are you actually able to look in the mirror and realise when you look good and don't look fat or whatever? If not, then I think you need to find someone else to act as your guide for that otherwise no matter what size you are, you'll think you're fat. Maybe speak to your husband?
And secondly, I don't think that it's advice from a website that you should be looking for. I personally think that really you should go and have a chat with your doctor. Explain how you feel at the weight you are now and what weight you want to be. He or she will sit with you and go through it all and decide what weight you should be aiming for. And if they agree that losing weight has a benefit to you (which it may not at this point as you are already considered healthy) then they will be able to help you put together a healthy plan to follow to do that. Or, if they think that actually you're good the way you are and that it's the eating disorder stopping you from seeing that, they can arrange some help to try and change the way that you see yourself so that you see yourself as how you really are instead of through the glasses of an eating disorder, which distort everything.
I hope that whatever you do, you find the thing that works for you and keeps you healthy. I don't mean to lecture you, at all, I just wouldn't want to see you hurting your body to lose weight that maybe you don't need to.
