i think you just took your first step: admitting that you may have a problem. step 2, call a therapist (or whomever you're supposed to call to get some help). step 3, tell your husband that you're wanting to put a stop to it, so ask him to eliminate all laxatives form the house for time being.
i don't think you have hit rock bottom, you don't have an unhealthy weight, and it's early enough for you to do something about it. be warned that if you don't take steps towards recovery this will take a hold of your life, which you cannot afford having kids, going to school, maintaining a healthy lifestyle.
yes, i fear weight gain because i have no thyroid. i am scared to death that even if i gain a pound i am stressing over it. but when that happens, and hopefully it never will, i will seek treatment, whether it is a trainer, a nutritionist or whatever. so your fear of weight gain, is normal, you doing something about it, when you don't need it, is not. seek help mama. hang in there