Well, you might get to Heaven, but it would only be through the infinite mercy of Christ, and in spite of your disbelief.
I am a Catholic (with Orthodox sympathies) and I think your comment strays uncomfortably close to Feenyism.
Is the Immaculate Conception not a dogma of faith? Does not heresy consist in the doubt or denial of any article of faith proclaimed by the Church? Is not formal heresy fundamentally contrary to the supernatural virtue of Faith, without which there is no salvation? St. Thomas affirms that anyone who denies even one article implicitly denies them all, by rejecting the judgment of the Church to whom it is given to interpret Holy Writ - therefore, he believes nothing but his own opinion. Feeneyism is a great error, but liberalism is its opposite and must also be rejected; the traditional belief on this matter is expressed quite well by Newman, Loss and Gain, p. 380-2:
"Then he believes himself, if we may so speak," said the priest, "and not the external word of God." "Certainly." "Well, in like manner," he continued, "do you think a person can have real faith in that which he admits to be the word of God, who passes by, without attempting to understand, such passages as 'the Church the pillar and ground of the truth'; or, 'whosesoever sins ye forgive, they are forgiven'; or, 'if any man is sick, let him call for the priests of the Church, and let them anoint him with oil'?" ... "Do you think these persons believe and practise all that is brought home to them as being in Scripture?" asked his companion. "Certainly they do," answered Charles, "as far as man can judge." "Then perhaps they may be practising the virtue of faith; if there are passages in it to which they are insensible, as about the sacraments, penance, and extreme unction, or about the See of Peter, I should in charity think that these passages had never been brought home or applied to their minds and consciences—just as a Pope's Bull may be for a time unknown in a distant part of the Church. They may be [Note] in involuntary ignorance. Yet I fear that, taking the whole nation, there are few who on this score can lay claim to faith."[Footnote:] "Errantes invincibiliter circa aliquos articulos, et credentes alios, non sunt formaliter hæretici, sed habent fidem supernaturalem, quâ credunt veros articulos, atque adeo ex eâ possunt procedere actus perfectæ contritionis, quibus justificentur et salventur."—De Lugo de Fid., p. 169.
And I don't think anyone would call him a Feeneyite!
I am sorry, but the Immaculate Conception is Catholic doctrine. As a Catholic, you're really not free to disagree with it. Doing so only works against your salvation.