Dear human, thank you for sharing and reaching out with your concern. It’s not easy to always share how you feel. It is completely understandable that you feel a lack of concentration and focus in your own life when your mind is preoccupied with the thoughts of your partner possibly being an infidel. It can be frustrating for many people in your position and uncertainty is not well accepted by humans. Since this is an internal conflict (within yourself), it is taxing on you and hence you find it difficult to take care of yourself. These negative and intrusive thoughts could be because of many reasons such as trauma events in your personal life, past negative events, recent negative incident with your husband, behaviour patterns of your husband, and many more.
My suggestion to you at present would be to seek professional help (therapy) to understand why you have such thoughts and what can be done for it while simultaneously trying to take care of yourself, monitor your appetite, sleeping-awake hours, and your will to do your daily life activities.
Next Steps
Please book an appointment with me via practo, as we go about discussing and identifying your thought patterns, possible reasons and ways to manage it.
Hope this helps :) Take care!