Based upon what you have stated, it doesn't seem like you are not in love with your highschool sweethart/ husband. It seems like you decided to get married and have children at a young age, now reality is catching up with you. In other words, it is natural for most women you start a family at a young age, feel like they are missing something. That absence is not worth losing your family. Study your husband to discover how you to sure spend some fun time together. Also, make sure it is not a money issue or concern with me, in which could be a reason he doesn't want to have fun.
Do you have anyone you trust that could watch your children? If so, plan a special night for the both of you, at the house, by getting creative. Once he get the feeling of how fun it is, to be with you solo, his desire will increase. It is so important for us women to study our husband's likes and dislikes, what turns them on and off, how to please him. Remember, we as women are teachers. In most cases then not, men need to be taught many things.