Thank you for reaching out. First you must identify how frequent is the thought and is it only one thought or different every time. Since you mentioned you have bipolar I am sure you are consulting a psychiatrist , you must seek his or her advice instead of using any medication on your own. Many times there are associated disorders with mental illness, which must be ruled out. What you mention seems anxiety . Kindly seek your psychiatrist advice and also psychological therapy will have very good impact on your cure. Thanks