Hello Abit,

First of all, you need to clearly understand "love something doesn't mean you must accept everything without any question or hesitation". We are all human being, we can't kill our emotion and JUST accept everything.
Knowing this is important because you need to know that you have to take initiative to solve this feeling, instead of suppressing it and hope it will eventually go away.

Second, you probably already know, everyone has their own sad past. She never ask for this, if there is a chance to make different decision that won't turn out like this today, she will definitely take the chance. So what done is done, the scar is already there. No one want this to happen, and she is the main victim here. Some more she has a daughter to bear. Since u say her ex husband only supporting her financially, it's hard for a woman to take of a child by herself while need to continue looking for her own happiness despite having a sad past.
Therefore, no expectation should occurred that she can throw away the responsibility of taking care of her daughter and continue living for your like an ordinary girlfriend.
On the other hand, if she just doesn't care about her daughter but all about her own happiness, will u still think she is a good person?

Then, you must understand another thing: loving a person means sharing happiness AND sadness with him/her. So, you need to talk to her about how you feel. Just remember that many people did mistakes by communicating message with emotion and trying to make others agree or follow what they want. So you need to know that talking to her means telling her that you felt insecure despite understanding she has a daughter to bear and she can't just behave like any ordinary girlfriend, however you do wish that she can behave like any ordinary girlfriend. Just tell her this, and then listen to what she think or want to say.
Keep conveying your message in a structured way and make sure your objective is:
1) Just to let her know how you feel, not asking her to help to create the solution that you want.
2) Listen her telling how she feel and what she think about your thoughts and feeling
3) Repeat the process of expressing feeling, stop & listening, think and expressing feeling based on feedback

Remember, your objective is to let her know how you feel and see if she has any idea to make both of your life easier.

Don't keep all these feeling into you, because it will eventually turn into grudge and depression.
When small argument go off between you and her, you might use this reason to explode but it's not fair to her.

For your working stress, do remember that it's YOUR work stress, we all have it. But no saying that the best solution is to look for our partner to release stress. So I would suggest you to look for friends and learn stress management in your own way.

Lastly, for your family side..... It's an unchangeable factor. Family disagreement is something that keep going on and on. You don't need to hide her background forever, it's up to you how you want to convey the message to your family member. But try your best to let your family member know how brave you are for accepting a person who had a sad past and how much feeling you gone through all these time, despite that you still decided to be with her.

You can drop me a message if you need someone to talk to