Hey everyone, I'm new to the forum and while I know this is a place for mums it's the only place I can really think of to turn for help.
I'll start by giving a background on our situation then talk about our current problems and hopefully can help get some things off my chest and maybe even get some advice from people who can give an un biased opinion on things. This might be long so please be patient with me 
I met my partner just over a year ago, I knew she had a 4 year old from the start. We fell madly in love very quickly and at first her child was never mentioned, it was just me and my partner dating etc. After about 2 months I was introduced to her son and we bonded very well immediately. After three months I was stopping at my partners house so often, everyone was getting along so well we both decided it would be a good idea for me to move into her place. In hindsight this was a huge mistake and we moved far to fast without talking over what my role would be and what we expected of each other.
Almost over night I became a married man with a 4 year old child, while I had expected to be a part of his life I had no idea to what extent and what she had expected of me. Suddenly everything has a timetable, the fun relationship was gone, I could no longer make time for my friends without feeling like my partner was unhappy about it, I had to sacrifice all my hobbies, pastimes and passions to put her and this little guy first. I'm a creative guy so suddenly having no time to make my music, edit videos and work on my blogs was very hard for me. My stepson still has a dad, who pays no child support, only sees him once every two weeks (if he even turns up) and at 33 years old still lives with his mam, he does nothing for his son.
I felt my partners expectations of me grew every day and I could never do enough to please her, I pick my stepson up from school when I can, I drop him off in the mornings, I split the bills for his food, buy him gifts and spend loads of time with him. I take him out just the two of us and try so hard to show my partner I'm serious about them but as soon as I put a foot wrong or get stressed about things my partner is straight on my case. It got to the stage where I thought "where does what I want come into this?". I feel like I'm expected to be a dad to my stepson, give up my entire life for him, provide for him and treat him as if he was my own, without getting any of the benefits or say that a dad would have and while getting nothing back in return. It's resulted in me feeling underappreciated, used and resentful.
These feelings started to leak out and my partner noticed and we had a massive row about things, I tried to explain why it has been hard for me and she became really defensive and said something like "what's so difficult about it", she made me feel like less of a man because I was struggling with things and in the end I went on a big rant about how hard it is to do what I'm doing because this child isn't mine and I get no thanks for anything.
Me saying " he isn't mine" is something that has never left her head since, she now believes I don't want him to be around and she feels like I've made her and her child feel like a big inconvenience and that I'm not suitable for this relationship. In the end she basically told me to leave. We cried, I promised I would try harder and in the end it's all came down to me to fix things.
So now we are in a situation where I need to make it up to her in order to save this relationship because she believes the things I've said about her son not being mine are very bad/offensive things and that I now need to prove myself to her. She's not acknowledging that while I didn't put my point across very well (and I'm sorry for what I said) what I said was said for a reason.
All my feelings are not considered and now if I want to save the relationship the ball is in my court. Has my partner put too much on me too soon? Am I being selfish? What role should a live in step dad play?
My head is in a mess and I don't want to loose my partner or my stepson but I don't want to keep feeling like my feelings don't matter and that I'm only here to serve her and her child.