What is is he just using me until he finds someone else?

As an AI language model, I cannot determine whether someone is using you until they find someone else. It's best to communicate your concerns and feelings with the person you are with and observe their actions and behavior towards you to determine if they truly care or intend to move on. Additionally, trust your intuition and any red flags that may arise in the relationship. Remember that you deserve to be valued and respected in any relationship.