I know how you feel to a certain extent. I have been living with my fiance for 18 months now and he has custody of his two kids 5 and 3. I have my own daughter who is 6 in Nov. Any we are trying for another.
I have struggled with your very issue. It is so hard taking in some else's kids. Do you have any of your own? How old are they?
Anyway, about 6 months ago I was in such a state that getting out of bed in the morning was an awful feeling because I new what was facing me. I was crying all the time, yelling at the kids for such little things and at times getting so angry I had to lock myself in my room because I was affraid I would hurt them. Stressed out about the smallest things. I remember one morning I burst into tears because my step son wanted porridge for breakfast and to me at that time, making porridge was pure dread, so I ran back into my room and cried.
To cut a long story short, i ended up at the doctors because I did't know what was wrong with me. I suspected it was Depression.
I was diagonised with Deep Depression and have been on antidresspants for 5 to 6 months and I feel so good. The kids no longer stress me out, I can look at a HUGE pile of washing and ironing and not cry and I don't yell at the kids anymore.
SO my advice is maybe go and see someone if you feel like I did. If not then my motto was then and is more so now 'Don't sweat the small stuff' If they are not going to break anything or hurt themselves or others then does it really matter. I found that if I was going to yell at them I closed my eyes counted to 10 and assessed the situation.
So in short, you have taken on such a responsibility that is hard for anyone to understand unless they are in the same situation. Don't beat yourself up sit down and take a good look at what is causing you to feel like you are - Is it really the kids. I say that because that worked for me. Otherwise there is a book called 1,2,3 Magic and a book Every Parent. They are great books for stop behaviours and start behaviours.
