All I want to do is cry.....
I am so happy I found this site after one horrible day that isn't even over yet. To make a long story short I have been with my bf for a little over two years and just a few months ago his 3 yo son started living with us full time. I was (and still am for the most part) happy that we have him now because BM is way too young immature and selfish to be a good mother right now AND just two weeks ago she decided to go back to her country without telling anyone or saying goodbye to SS or her other BS....she is such a mess....but anyway from the time SS was living with BM and when he would go visit her before she left he picked up A LOT of bad habits like screaming throwing hitting and now my bf and I are left to deal with it. It is especially hard for me because when I try to discipline him he starts screaming for BM and it is so overwhelming for me. I know temper tantrums are normal for 3 yo but it's so hard to deal with them and him screaming for BM when I feel like his temper is partially her fault to begin with. I took the day off from work because I have a final tonight and instead of studying I've spent the day getting hit and giving timeouts. I'm exhausted and can't wait for my bf to get home but then I have to go take a final 
Does anyone else have any problems with discipline and their skids??
Just be thankful that you
Just be thankful that you have him and are able to teach him whats right and wrong. I would give anything to have our 3 SS-11 and 2SD 9,7. The BM has tought them that they do not need to shower everyday or how to properly get dressed and they have no manners. We (mostly me bc my husband does not pay attention to stuff like that)have to constently get on them when we have them to takes showers brush teeth comb hair deotorant all the basic hygine stuff that my 11 and 9 year old should be doing without having to be asked and when someone is speaking to them when we are out in public they ignore them. IMBARRISSING on my husband and I as parents and what a great way to spend the 1,3 5 weekend with the kids always being on their butts.
Believe it or not, like the
Believe it or not, like the other posters said, it is so much easier because she is gone.
3 year olds are rough because they don't have the capacity to rationalize.
The only thing you can do is time outs and association - dare I say it, like a dog. If he does something good like uses his manners, give him an animal cracker. If he is having an awful violent tantrum, put him in time out (we used to have to put SS9 in his room and take all his toys out).
If it makes you feel any better, our youngest went through this too at the same age because he was bounced from home to home - until DH won custody.
So I guess what I am saying is, you will be okay.
Try to take one day at a time and know that it isn't forever and that he can still grow up and HE IS NOT HIS MOTHER. He is his own person, with your help of course.
Be thankful she is gone and
Be thankful she is gone and you have plenty of time to raise him right. He is only three and trust me I didn't even like my own kid much at that age. We didn't go out to a restaurant for almost a year because of the temper tantrums. Now he is a normal 15 year old in all honors classes that wants to be a doctor. It does get better. But, I had days like that where I couldn't wait for his Dad to come home so I could walk out the building. I gave birth to him so I can imagine your frustration, because he isn't yours. Just know that it does get easier. Around the 5 year mark, he was such a joy again...
If you can try and think of
If you can try and think of how you would feel if you could not express yourself in words if he/she can talk and not only that "YOUR" child is trying to deal with an "adult" situation which a child should never have to exprence. I know times are tough but if you can when a tantrum is going on and you know that it has to deal with the loss of BM HUG your SK and try and hold him/her. A hug says so many words and let your SK know that IT IS OK to feel the way he/she is feeling and that YOU are ALWAYS going to be there for them. You have a HUGE advantage going for you with BM out of the picture and your SK being so young, you can and forgive me for saying it like this but REPROGRAM him. Also have plenty of wine on hand!!!
I promise it will get better!
I promise it will get better! I went through the exact same thing. i had been with bf for two years when mom decided she did not want sd anymore and left her with him for good. He all of a sudden went from a weekend dad to a fulltime dad of sd3. I panicked i cried i ran. We actually kinda took a break to see if i was happy without him. i was miserable though. therefore i went back to him after one month and decided it was worth it to be with him. she was a holy terror though. slapping, hitting, screaming all night. now she just turned five last week and she is a really well behaved kid. it wasn't easy but we made it through it. Now i have a pretty well behaved sd and the husband that i wanted. so just be strong. take a time out if you feel like it is too much!