I feel awful saying it but at the same time i also feel like i have gotten to the point where i don't know what to do anymore.

My partner has his son who is 4 years old every weekend and i have my son who is 7 years old always as his father passed away. We got together a year n a half ago.

At first when we integrated our families together it was great! We knew it would be easier for us as our children already knew each other and we already has some kind of relationship with each others child before we became a couple.
I realized very quickly that me and my partner had very different types of parenting, he gave his son what he wanted when he wanted, where as i was more structured with rules and boundaries. I understood why my partner was so lenient, as his weekends with his son was all he had to look forward to but i also knew it would bite him in the bum one day too.

My Partner's son behavior has been a issue since we got together but being so young i took it for what it was, his age! but i also noticed other things, he wasn't taught any manners which i soon changed, he wasn't use to sharing anything and wanted EVERYTHING his way, he was rude and disrespectful but not because he meant to be but because he wasn't taught anything different.
I spoke to my partner about this behavior and where it would lead to, he felt the same and he told me what my step-sons mother is like, a Lazy, rude, selfish excuse of mother who will take no responsibility for her sons behavior and will teach him nothing and will dump him off to whoever she can, at first i thought he was over exaggerating until i saw this behavior for myself, but i also told him he was to blame also.

This was a challenge that i was more that willing to help with until my sons father passed away last year, since then things have been getting worse and worse for me and my son.

We can't spend any time together on the weekend unless we leave the house, my son has to put up with my partners son screaming and whining over silly little things like, my son touched his bed, it's gotten worse lately, my partners son has started making up lies about my son, saying he's hurt him, misbehaved when he hasn't and whenever my step-son has said these things I've always questioned my son firmly as i know my son's dislike for him and the fact that my son is NO angel! i'm hurt and upset when i find out the truth that my son hasn't done anything, i feel it's going to get to the point where my son is angry at me and doesn't trust me because of it. Our weekends have become unbearable, i never look forward to them and neither does my son no matter how positive i try to be.

Some of my step-sons behavior has rubbed off onto my son which i am furious about and now with starting up lies i feel i cant trust him around my son and i'm scared in case the lies get more serious and social services are brought to my door or something, its trouble me and my son don't want nor need.
My partners ex has already has social services due to inappropriate things my step-son did and said, the blame was put on my step-sons friend but now i'm worrying in case this little boy who got the blame actually did anything at all?

I dont know what to do anymore, i've been awake since 2am worrying about it. I love my partner so much but i dont know how much more of this i can take? Every weekend is the same and me and my son cant even have 1 weekend a month where there is no step-son.

i know i sound like an awful person.