I, too, am a step-mom and my younger step-son was also ADHD. I know how trying that can be for a young woman, as I was only 25 when I married my husband, and my son was 10. (MY four from my first marriage were 5 and under) It's not easy being a parent, and being a step-parent, no matter how sweet the kids are, is that much harder. A lot of people assume that ADHD is just an excuse for badly behaving kids, and I'll admit that until I came to know and love my son I was one of them. Back in those days, I found that I initially had very little paitence for my son, and often yelled at him out of sheer frustration, which generally meant that he reacted badly and acted out in some destructive, hyper way... from writing on the walls, shaving off his eyebrows, running maniacally throughout the house, teasing and provoking his siblings... the list goes on and on. He was on medication but often "tongued" it, meaning he pretended to take it but really did not, and was very adept at faking it! What worked best for me during that time was absolute structure. I found that if planned out the days down to the last hour that he was at our house, he responded very well. He knew in advance what to expect and what was expected of him. It was the chaos and uncertainty that he was reacting to. It's not an easy solution, and requires a lot of effort on the parts of the rest of the family, but it really worked for us. I'm not saying that it was bliss and perfection after that but things really did improve in our home after that. Also, if you haven't taken him to be evaluated, then you should do that ASAP. He may need to be taken to a developmenal specialist, and you should be able to be referred to one through your primary care physician. Until then, hang in there, sister! You are truly an amazing young lady with a generous heart.