Hard to handle

Ok a little back story I was married for 6 years then in 2010 my wife cheated on me and we separated After 2.5 years were finally divorced as of this week. We both life in different states and are the same age. We got married when we were 22 and she had a 2yr old son from a previous relationship. So I was step dad from 2-9 and now hes 11. When she left I was crushed and separated myself from both of them out of anger. after 10 months I was dating and so was she and I got lonely and called out of the blue and we meet back up xmas of 2010. After that I realized all the anger was still there with her and took it out on him as well. fast forward to june of this year he called me out of the blue and it cought me off guard. he loves the new guy my ex is seeing but still calls me daddy and misses me and cried on the phone it made me feel an inch tall. now that were close to xmas again I decided to buy him a present and will ship it to him soon to put under the tree. My dilemma is I dont know how to explain to him that i started off life as his step dad. he found out about his real father but doesnt care its still all about me. Now I enjoy being single (now 31) and am moving on with my life as she is. shes already engaged and pregnant with new guys baby. Is it wrong to still send gifts because I care? How do I explain I can be a friend not a daddy? I wasnt good at raising a step son ex never let me was always her way. someone please give me some advice and dont bash on me I know its not the childs fault and I made my decision and am going to stick to it. I dont mind every once in a while call or email with him but not daily. It sounds mean but I loved him more in the beginning and eventually we grew apart just as ex wife.