I have posted on here before but I wanted to post an update on my situation and hopefully get some advice.
I'm in a mess. I have been with my DH for 2 years and 2 months (we have been married for 6 months). I never should of married this man despite the fact that I am deeply in love with him. He has a child from a previous relationship. sd12 does not see bm. bm is psycho, in jail (currently) and basically the scum of the universe. sd12 lives with dh and myself all the time.
A lot of her problems are consistent with ADHD and Aspergers so she has been seeing a psychologist who has not made a diagnosis. I still believe there is something seriously up here. Anyway to list a few ..

*Constantly interrupting other people’s conversations and butting in changing the topic to something completely irrelevant or inappropriate.
*Constant need for attention.
*Does not like spending any time alone and wants to be around other people all the time.
*Does not understand people’s needs for personal space and privacy.
*Constant talking. Does not know when appropriate to talk and when appropriate to be quiet. Often makes constant verbal sounds on her own talking, singing, and other verbal noises which make no sense.
*Difficulty making friends. Relates better to younger children and adults. Does not have many friends her own age and struggles to make friends her own age.
*Hyperactivity.
*Forgetfulness.
*Often forgetting and losing personal items such as shoes, jumpers, bags etc.
*Laziness. Does not want to do anything she doesn’t want to do unless made to do so.
*Lack of hygiene. Often won’t shower/ brush teeth etc unless being reminded to do so.
*Lack of resilience in getting over minor things going wrong. Acts like it’s the end of the world when nothing major has happened (on a regular basis).
*Low and high moods, from one to the other very quickly.
*Very anxious when she does not know exactly what is happening. If there is a routine she can cope a lot better but if she doesn’t know what’s happening there is a high level of anxiety.
*Constantly asking questions one after the other.
*Unable to be pleased. If you do something for her she just wants more and more and is never satisfied.
*Extremely clingy. If there is a large couch with someone sitting on it she will always sits right next to the person not giving them any space at all instead of sitting on the other side of the couch.
*Lack of respect for adults. When disciplined back chats, slams doors, yells, tells her father ‘I hate you’ etc.
*Lack of sense of time. Doesn’t seem to be able to tell whether it’s been 5 minutes of 5 hours or sometimes what time of the day it is.
*When told not to do something many time she continues to do the same thing over and over and over. Struggles to change habits. We can go over the same thing with her 50 or 100 times and she still struggles to change the habit. Forgetfulness and laziness also comes into this.
*Tries to dominate social interactions with groups by trying to get the attention back to her and interrupting people’s conversations. She is happy to have the complete undivided attention of one person but if she doesn’t have one person’s attention she is constantly trying to get one person’s attention back to her in a group situation.
*Often relates better to animals (dogs, cats etc) than people.
*Often copies and mimicks other people as she is unsure how to act or what to say.
*Occasional sleepwalking
*Forgets basic things like flushing the toilet and taking tissues out of pockets before putting things out to be washed etc.
*Clumsiness
*Unaware of how loud she is and often talks very loudly or has TV, computer etc. extremely loud.

These are just some of the things I am dealing with with this child regularly. I have been trying to parent her for over 2 years and she is unable to fix even the most minor basic things.

The worst part is that I am 30 this year and feel I can't have any of my own children in this awful situation. Plus there is no room in this house so because of sd12 we have to move to a bigger house that we can't afford if there is even a possibility of me having kids.
All I want is to be having my own kids and I have to deal with this brat every day who is turning out exactly the same as her bm.
I'm so over this. I can't do this and I don't want to do this. I'm so stressed. I'm trying to hold down a new job I got this year but I have had to have surgery twice which I believe is mostly due to the stress this child has caused me as I have not had these health issues in the past.
DH talks about getting a bigger house and sd12 spending more time at her grandmothers house (that's another story, dh's mother is a complete nut case as well), so I can't say he is doing nothing but it just feels as though this situation is getting worse and worse despite our best efforts.
This child is nothing but damage but he can't see that. At this rate he will end up happily ever after with sd12, a lonely old man and drinking himself to death. Seriously, I'm really starting to think he does not deserve me at all. He definitely doesn't have my best interests at heart. I wish I wasn't so attached so I could leave. I honestly don't know how I'm ever going to get out of this. I feel so trapped and stuck

Any advice ?