Firstly, NO! You are NOT a bad person for wanting that at all. It is really hard when you break up, whatever the circumstances.
But I think you need to think really carefully about things, it's easy and natural to miss someone when you break up and blame all your bad feeling on the breakup itself, but think about it - things couldn't have been that great when you were together or you wouldn't have split, if you get back together, for it to work, something needs to have changed. If it was outside circumstances making things tough then maybe you both need some time apart to work through that stuff, then once that is over if you do get back together you will be stronger for it. Or if it was issues within the relationship making things hard, then be careful not to look back with rose tinted glasses.
Remember that you deserve to be with someone who enhances your life, makes it easier, makes you happy, not someone who makes life difficult or makes you feel down, even if that is only some of the time. You deserve someone who adores you, admires you and loves you for the beautiful, amazing, unique woman that you are, sees you as a true equal (and partner in crime 
) and someone who you feel a real team with, that you could do anything as long as you have each other's support. Whether that person is him, or whether it's someone else, I can't tell you, but you will know, deep down. Don't ever settle for anything less.
As for being a family, it's absolutely fair and natural to grieve for the family you have lost, please give yourself time. But please don't get too hung up on the two parents thing, you and your boy are still a family. I actually think it's fab being a single parent to one child, it can be stressful, but because there are two of you, you are forced to get along and the result is a lovely, co-operative relationship where you are more like far-apart siblings than parent and child, and nobody can ever take those special times away from the two of you.
Things are going to work out okay. Be kind to yourself, first.