Yea you did get married too young, you should be living it up and college and not dealing with issues like this.
It doesn't sound like you guys hang out much or have fun together. Do you have access to a babysitter? You guys need to reclaim your youth before it is gone. What do you like to do, what does he like to do?
Is he worried about finances? Being financially responsible for a family of 4 at 21 is huge, as is being a SAHM to two small kids. You guys really need time out.
I would suggest marriage counselling to deal with the lack of communication. Talk to your local pastor or equivalent and see what?s available in our area.
In regards to sex, does he know that you are not satisfied? Do you know how to orgasm by yourself? If you know how to orgasm, show him what to do. It is as simple as directing his hand and responding positively to every touch. Men love to hit a home run, I bet he will be more than willing to try.
Remember it is not up to him to initiate conversation, fun or make you orgasm. You are responsible for your own life. Take the lead, ask him how his day was, dress up in something sexing and show him how to turn you on.
Open the conversation up by telling him you are feeling a little detached lately and worried that you guys settled down to early. Ask him what his thougths are. Think long and hard about what you want and tell him. You say he never surprises you anymore, do you surprise him? Tell him you would like him to watch a movie with you once a week and surprise you with flowers once a month or whatever. Just as importantly ask him what he needs to make him feel special and connected to you and do it.
Inject a little fun and spontaneity into your life, your only 21 for god sake.