I used to deal with severe intrusive thoughts. Firstly, don't ever try to push the thoughts away no matter how much you want to. When you push, the thoughts will just push back and come back stronger.

The best thing you can do is to allow these thoughts to happen, witness them like any other thought and practice deep breathing. I had to do this exposure exercise with the help of a very good psychologist at first, but I was also able to practice alone. Therapy with someone who understands intrusive thoughts could be very helpful, if you are able to get access to that.

Once you force yourself to witness these thoughts without fighting back for a while, they will cause less and less anxiety. Eventually it won't cause any anxiety at all. Some days will be better than others, and be kind to yourself on the bad days especially.