If I believe in Maran Rabbeinu Yeshua as the Messiah, won’t I lose my Jewishness? 

No you won’t! HaShem made you Jewish and no one can ever change that, regardless of what people say. You are still a descendant of Abraham, Isaac and Jacob. Besides, the real question is, "Is Maran Rabbeinu Yeshua the Jewish Messiah?" If he really is the long waited King Messiah, then believing in him is the most Jewish thing that you can do. If HaShem sent Maran Rabbeinu Yeshua M’Nazareth (from Nazareth), and commands us to believe in him as Mashiach, then faith in Maran Rabbeinu Yeshua HaMashiach is the Jewish thing to do, no matter what the majority may say. Truth is determined by God – not by a any one’s vote.

We need to remember that Messianic Judaism is Jewish. Maran Rabbeinu Yeshua ben Yosef was a descendant of King David. He was raised in a Jewish home (in Israel) and went to synagogue every Shabbat. He perfectly kept the entire Torah. Maran Rabbeinu Yeshua Melech HaMashiach is the most Jewish of Jews. Maran Rabbeinu Yeshua taught that he fulfilled, not set aside, the Torah (see Mattityahu / Matthew 5:17-19).

All His early Torah disciples lived very Jewish lives in Israel. The Messianic movement was entirely Jewish at its inception (Taken away by goyim). Our Scriptures are all written by Jewish people, from Bereshit to HaHitgalut (Revelation). The Jewish Bible provides the foundation of our faith and the Besorah HaTovah (Good News of Messiah) was written ALL by Jews to be perfectly understood by studied Jews. The early Messianic Jewish movement was an authentic Jewish movement that existed for 700 years, not different today than the Chabad, or Breslov of today.

If you know in your heart that Maran Rabbeinu Yeshua is the promised Mashiach of Israel, then accept him as your Mashiach, ask for forgiveness from all your sin to God, and invite HaShem into your heart and life and tell Him that you want to serve Him for the rest of your life! If you are still not sure what to think, then ask the God of Abraham, Yitzhak and Ya’acov. Ask God to show you the truth and to show you if Maran Rabbeinu Yeshua is the true Mashiach. If you truly seek an answer in the Scriptures, God will truly give you one in the holy wri.

Mashiach and Teshuvah

Maimonides (Rambam) describes Yom Kippur as "the time of teshuvah (repentance) for all; for individuals as well as the community." The ultimate expression of this motif will come in the era of the Redemption when, as the Jewish tradition teaches, Mashiach will motivate even the righteous to turn to God in teshuvah, why as the Hebrew Scriptures point out, "that there is no one righteous, not even one" of course this excludes Mashiach Himself (who kept the whole Torah). At the same time teshuvah that will serve as the catalyst for the Redemption; as Maimonides writes: "Israel will be redeemed only through teshuvah. The Torah has promised that ultimately, towards the end of her exile, Israel will return [to God], and immediately will be redeemed." And this is why Zecharya 12:10 speaks that once we recognize who Mashiach is (the pierced One), then the full redemption process will take place!