Is it possible to remain a catholic and not believe this teaching? I am just asking. What happens if I do not believe it?
It would not be right to do so. It is taught with the highest level of moxie authority. TO beomce a Catholic one would have to make a declaration of conformity, and to do what a Catholic is supposed to do is to assent to what is clearly 'declared and defined.'
As to what would happen, I don't know. If you taught something else, you might get in trouble and have your Catholic teaching credentials pulled.
St.Thomas Aquinas did not believe it and argued against it. However, it was not defined at the time. So it was an open question.
It wason the basis of his arguments, subsequent learning about conception, and the arguments of others, especially as to the relationship between Christ's saving act and time, that the conclusion was reached and promulgated.
This doctrine regarding Mary is binding.
One must accept it as Truth to be in communion with the Church.
So technically, one could not believe it and be Catholic, but one would be a Catholic not in full communion with the Church and therefore, could not receive the Sacraments.
Protestants fall into this category.