Will I be considered for custody?

My husband and I divorced last year, and because I stayed at home with our son while we were married, when we divorced I had no job and had to move in with my parents. Now before you get on me about not having a job, that was the option that we decided was best as parents in our situation. And within a month of our separation I had a full time job. Well because of my situation I thought it was in my sons best interest to live with his father with me getting to see him whenever I wanted. About 2 months ago my ex started dating again and has become quite serious with this new woman. My son met her 2 weeks ago and she's already spending the night in their home. Maybe I'm old fashioned but this is something that bothers me. I currently have a boyfriend, and while we (my son, myself, and my boyfriend) do things together, it hasn't evolved into overnight stays as I think it's too soon. My son is 6 by the way. Anyways, this morning my ex sprung the news on me that before the school year started he was planning on putting his house on the market and moving about 40 miles away to be closer to his job and girlfriend, and putting my son in private school. While I'm not opposed to private school, and I know that 40 miles is not as far as say 300, myself and all mine and my son's family is here. All within 10 miles of each other. Aunts, uncles, cousins, grandparents...all with whom he's grown very close to. I would like to take him to court to have residential custody over our son, because I feel like this move isn't taking him into consideration, but more thinking about himself. The school he's currently in is fine, the neighborhood is fine, and the house is plenty big. But he's already expressed that if I did that he would fight me on it. And unfortunately his resources are much more unlimited than mine. I feel like I can provide a safe, stable environment just as well as he can, just maybe not with all the luxuries. I do live with my parents, but in a 4 bedroom house, and have a stable job. I'm not a druggie or an alchy. I guess what I'm asking is 1. Am I being unreasonable? and 2. Do I have a chance of getting custody?