What Can I do?

I had my son in April 2004. I had JUST turned 18 and was 4 weeks away from graduation. I gave birth to him on a Thursday and was back in school on Monday. Neither here nor there.I tried as hard as I could with little to no support for a year and a half before deciding to let my high school parenting teacher and her husband adopt him. He is now 5, almost 6. Due to my ex, my sons father, the adoption process took a very long time. He was almost 2 when they initially took him in but 4 when the adoption finally went through. I was told that the adoption was going to be open. I didn't put any stipulations down when I signed my rights away. I was told several things that have not been kept up, even with my reminders. I was suppose to be able to talk to him on or someday close to his birthday every year, see him once a year when we were in state and I was told I would be receiving a letter and pictures once a year with all of his new achievements listed. Since the adoption has gone through, my husband and I have had a beautiful daughter. We sent Christmas letters out to all of our family, including my sons family. With their letter, I sent a personal letter to my boy. I called to ask if they received it and get worried when I got no answer or no reply for a couple weeks. I called my mom (My foster mom from the time I was 12 to the time I graduated) who is very good friends with the A-moms mother. I find out they have no intention of ever telling him of my daughter or giving him any letters I send him. They don't want me in his life and will do everything they can to deny that I exist. I was also told that they wanted to adopt my son because they couldn't have children of their own. That it was impossible. Only to find out that when they had me sign my rights away, they were 4 months pregnant.Checks that I've sent twice a year for the last 2 years to be turned into bonds have never been cashed. Packages I send for his birthday have been returned. I guess I should have seen this all coming. I didn't even know that the adoption went through until a week afterward when I heard it from my mom. Because of this, I have started a box/bin for him. Letters that I write I keep a copy of and put it in this box. I don't send gifts anymore, and any money/check that I would write for a bond, I put in an envelope and keep it in a safe. I know he will look for me, and when he finds me, I will not look like the abandoning mother they've made me out to be.I've been nothing but lied to by this family. And it breaks my heart that I was deceived by someone I "knew" I could trust. I don't want to "take him back". I understand from years in the foster care system that uprooting a child is seldom good. But is there anyway I can revise the adoption stipulations?? Is there a way to make the things they gave me their word on, in writing now, so that they're required to??