My husband has another child, why am I jealous feeling?

So, my husband and I dated for three years, then we split up for two and a half years. We got back together, and we became pregnant and were married six weeks later. I love him dearly and do not regret anything but-- while we were seperated, he was with this girl, she became pregnant, and he then learned that she was cheating on him so he made her move out. She then, went to be with the guy she was cheating on him with and told my husband that the child was not his. We went on with our life but we got tired of hearing about how the child looked jsut like him so we went and did a paternity test. COme to find out, the child was five months old, i was eight months pregnant and the child was his. So we pay our childsupport weekley (taken right from his paycheck), we cover medical, we pay co-pays adn we get this child every other weekend, and every Wednesday. Sometimes i am okay with this, but many times I am not. Sometimes i am Jealous and others i just hate that my husband was this stupid-- she has three kids by different dads and is now pregnant again-- i hate that our family is even associated with her. I know that its not the child