I would encourage you to tell something like this to God: These are not my thoughts. I refuse to accept them as my own. I choose to not be afraid of these thoughts. I give you any and all anxiety that comes with these thoughts. Thank that you love me. Thank you that you don't condemn me.
If you are truly not sure if these thoughts are coming for your heart, and I highly doubt that they are, ask God about it. Ask him to reveal any wickedness or if there be anything in your heart contributing to these thoughts and to show you what to do about it. If he does not show you anything in your heart then it is not coming from your heart at all.
Please don't try to fight away these thoughts, as bad and anxiety provoking as it may be. In doing this, it will only make things worse for you. As you accept the presence of the thoughts( not meaning you enjoy them in any way) and as you don't fight away the thoughts, the bad thoughts may increase for a time but after a while it won't be as bad. I am not guaranteeing that you will never have the thoughts again. That is unlikely. But I do believe that as you let the thoughts be there, not dwelling on them, but not trying to forcefully get them out of your mind, things will get better.
Dwell on God's love for you. Read about his love. Celebrate his love in song and worship God.