Ringing each other's necks, I need help ASAP! Can you please help?

My dad and stepmom have been married for a little over a year. Things between me and my stepmom were great, I got along with her well. Later on, we were constantly at each other. She used to call me foul names and I would argue with her constantly. I got counsiling to help lower me arguing completely and for some reason, things were a little bit better without my dad yelling at me for arguing but my stepmom put up higher defenses. A few weeks later things had worked up so much I threatened to leave home to live with my mom. My mom had told my stepmom that the foul names had to stop. She did. I still live with my dad and stepmom. But no matter how hard I try I still end up doing something wrong that makes her upset and creates her to "cry". I try to help out with everything including the baby but it's still isn't enough for her. Is it me? Am I doing something wrong?