I really believe the vast majority of women who have had a mastectomy have a hard time dealing with the different body. I truly think that it gets better with time. You are going through a real trauma. Try not to beat yourself up about it.
Please look for a support group in your area. Contact the cancer society. Support groups can really help a lot. No one else can understand what you're going through.
Many prayers and hugs. You can do this!