What Is The Cause And Treatment For Vaginismus?

Hello! About 5 months ago my gynaecologist diagnosed me with vaginismus as I was not able to be penetrated due to anxiety. I have recently overcome part of the issue, my boyfriend can now insert his whole penis in me without pain, however it does not feel good and it also makes me feel like I need to poop. This issue has continued despite the different positions we try. What is wrong with me? What should i do to fix this issue? Thanks.