I want to get engaged, but I dont know if i should...?

I accidentally started off my adulthood prematurely. I got pregnant at 15, and had my son at 16. The father and I were both in a REALLY bad spot in our lives that consisted of drugs and nothing more when I got pregnant. Needless to say, when I chose to keep my son, I made him my number one priority and from that point on my entire life has revolved around him. I finished high school, I quit everything cold turkey, I got two jobs, I started college, etc. His father was not ready nor willing to accept the responsibilities of being a parent and bailed out within the first trimester of my pregnancy. I had no intention of dating, like I said, my son was my main focus. However, a good friend of mine stepped in to be a part of my loving support system, and he stood by my side throughout my pregnancy. I had never even thought of him as the boyfriend type because before my son, him and I lived completely different lifestyles. I partied, he studied; I (almost) dropped out of high school, he is going to college and graduated with honors; I was bad, he was practically angelic. Anyways, he waited in the hospital waiting room with my dad when my son was born, the two of them pacing and shaking with nerves. He took time off work to stay with me (we camped out in that same waiting room) when my son was admitted to the Neonatal Intensive Care Unit for a week even through New Years. He asked me out numerous times but I turned him down again and again because I didn't want to start a relationship before I was able to get situated in my new role as a mother. After a few months though we made our relationship official and have officially been together over a year and a half. We are living together and he is raising my son with me. He is the best father I could have ever asked for for my son, and the most amazing person I have ever met. We argue occasionally, but he is always willing to compromise and we never go to sleep without first resolving the issue. Our communication was rocky at first, but we have almost perfected it (although I don't expect it to ever be perfect). What matters is that we are able to work as a team to overcome obstacles. We love and respect one another. My relationship with him is unlike any other relationship I have ever had. Mostly because my other relationships consisted of two incomplete people meshing together trying to fill each others voids. But my pregnancy both forced and encouraged me to move in a positive direction and become a complete person. Now my relationship consists of two complete people who compliment one another and encourage growth and personal success. He is my support system, he is my best friend, he is the person I confide in, laugh with, cry with. I am shameless around him because even in my worst moments, my weakest moments, my most embarrassing moments, he still loves me. I already know that I am going to spend my life with him. My mind can't even conjure up a picture of my future without him. The only thing is, I am still only 17 (I turn 18 in July). My family and friends all support our relationship wholeheartedly, but because I had my son so young (even though he was a blessing in disguise and is loved immensely!) I feel as though I am somewhat of a disgrace to my family and I am afraid of making another big decision too soon. Of course, the timing is ultimately up to him, and we have already agreed to wait until after I turn 18 to get engaged, but we have already picked out the rings and I know it is something we both want. We probably will be engaged for at least two years before we actually get married. I am completely confident about spending my life with him, I guess I am just worried about what other people think. I know I shouldn't care, but I made one big mistake and have devoted my life to my son which has made everyone's standards for me a lot higher. I just don't want people to look down on me again. I want to get engaged when I know people will be happy for me and supportive of my decision.