What does it mean to follow one's conscience? Is it a thing where it's a sin not to follow one's conscience? For example, would remaining in the Catholic faith even though you believe entering the Orthodox one makes the most sense to you, be a betrayal of that conscience and become a sin?
I'm just unsure about how far one can take the whole "follow your conscience" teaching and what it actually means.
Yes, an erring conscience binds us. St. Thomas Aquinas (see ST I-II, q. 19 a.1) and St. John Henry Newman are among those who note this. Of course, we may or may not be culpable for a malformed conscience. If you conscience told you it would be a sin to stay Catholic, then you would have to join the Orthodox communion. Whether that is equivalent to the Orthodox faith "making the most sense to you" is something you can only determine. Basically, you have to have a relatively high degree of certainty (though not absolute certainty). And I would not personally use the phrase "making the most sense" to describe a conclusion that I must follow or else fall into grave sin.
I suggest you pray this prayer by St. John Henry Newman:
"O my God, I confess that Thou canst enlighten my darkness. I confess that Thou alone canst. I wish my darkness to be enlightened. I do not know whether Thou wilt: but that Thou canst and that I wish, are sufficient reasons for me to ask, what Thou at least hast not forbidden my asking. I hereby promise that by Thy grace which I am asking, I will embrace whatever I at length feel certain is the truth, if ever I come to be certain. And by Thy grace I will guard against all self-deceit which may lead me to take what nature would have, rather than what reason approves."
A related questions that is being discussed in the Church (though not in your case) is the fact that a conscience only binds that person but no one else. For example, if your conscience Wheely told you that you were morally obligated to physically assault me, you would be obliged to try. But your conscience does not bind me to let you assault me, and it does not bind anyone else, so they may attempt to stop you in committing the assault. If someone doesn't believe they are sinning when disobeying the Church, they can in good conscience attempt to receive the Holy Mysteries, but that doesn't oblige the hierarchy to allow them.
But Cardinal Cupich, for example, has argued it would be prudent in some cases to allow such Catholics to receive the Sacraments all in the name of conscience (he explicitly mentioned the civilly divorced and remarried and also implies those who action disordered same-sex attraction impulses). He famously quipped: "the Church is called to form consciences, not to replace them." Which is a truism since the Church can not literally replace a person's conscience and of course is correct. But it doesn't address the question on when the Church should hinder the expression of a(n) (erring) conscience. More conservative bishops protested noting (also correctly) that the free expression of conscience has limits, but typically in their public statements, they have not gone into detail.
And now with the Covid Vaccine and conscience rights, the tables have turned. +Cupich and others have said no to people seeking exemption from vaccine requirements based on conscientious objections because the common good requires that as many people need to be vaccinated as possible. And some other Bishops who were skeptical of conscience exemption for Holy Communion are singing a different tune in praise of the inviolability of the conscience when it comes to vaccines. It is very much an ecclesiastical whiplash. It is a question that Church needs to address. Vatican II touched on it a bit in Dignitatis humanae. And the Patristic witness is a bit contradictory.
Thank you for the reply Devin. At the moment I'm reading "His Broken Body" by Father Michael. I find his arguments very compelling for the Orthodox position and simply believe he's right. But, at the same time, I'm suffering from confusion as to whether or not I'm making the right decision. I seem incapable of ascertaining what exactly a high degree of certainty looks like. I'm due to be Chrismated in 2 weeks along with my family but having doubts. Are these doubts normal and would proceeding with such a doubtful mind be considered an erring conscience that binds me?
Thanks for all the advice so far and the prayer is perfect thanks.