Kohen Firstborn Son After Miscarriage

Hi Rabbi, all my life I grew up thinking I was a Bechor (firstborn son) of my family, but recently I found out I’m not. As I studied halacha a lot more I found out that Bechorim who weren’t born naturally are not technically Bechorim. This destroyed me. I’m a huge learner with regards to the Mikdash and it was always my dream to serve in it. After learning from the sages that Bechorim will serve in the third Mikdash with Kohanim and Levi’im I was very excited. Then I heard that a Bachor that was born through the means of C section doesn’t get the same privilege as a Bechor born through traditional birth. I decided to find a way to halachically and historically prove that Bechorim born through C section birth also serve in the Mikdash. I wanted to ask the Rabbi’s opinion on this. Is it possible to come up with halachic proof of this when a lot of the commentators go against it? What do you have to say about this? Am I a Bechor in terms of future serving in the Beit Mikdash or not?

It is very inspirational to hear how passionate you are about serving in the Beis Hamikdash, and may Hashem hear your words, that even today so deep into galus there are people like you that look forward so much the rebuilding of the Beis Hamikdash, and may this be a zechus for all of klal yisrael to see the geula soon.
Its true that we find regarding many halachos that a bechor born through c-section doesn’t have the same bechor status as one born naturally. At first thought, the primary example would be pidyon haben, that a bechor born through c-section doesn’t need a pidyon (bechoros 47b, S.A. Y.D. 305:24).
On the other hand, to the best of our knowledge, we don’t know of any clear source regarding the avoda of the bechor that a bechor born through c-section doesn’t have the same status. (if you know of any such source, we are interested to hear).
In fact, it seams that it is unclear among the different commentaries as to exactly what kind of bechor did the avoda (before it was given to the leviyim). There are many commentaries who say that it was a bechor from the father, and not the mother. According to this, there is no reason to assume that a bechor born through c-section should have any different status–only regarding the bechor of a mother which has a status of “peter rechem” can one say that if he wasn’t born naturally then he is not the first of the rechem, but regarding the bechor of a father it shouldn’t make any difference how we was born.
Moreover, it is evident in several sources that the bechor who did the avoda wasn’t literally the bechor-it meant the greatest/oldest of the family. There are even sources that say that a boy born after a girl had the status of bechor for avoda. According to this, a first-born boy born by c-sections should all-the-more-so be considered a bechor for avoda.
We have included a few sources that discuss/mention some of these points. We apologize for not putting it all together more clearly, but we hope this will help you.
The bottom line is that you certainly shouldn’t jump to any conclusions that a bechor born through c-section is not considered a bechor, and there is strong evidence to show that he can do avoda.
May Hashem hear your tefillos, and may you be zoche to serve in the Beis Hamikdash soon.
If you have any more questions, or we can help in any way, please just respond to this email.
All the best
Rabbi Shay Tahan