I did tauba. Is it a shirk. And if it is, how should I repent.
Asalmualaikum brother, Saying Isa bin Maryam is what Allah has named him. His mother was Mary so your only saying that. So it should be no problem, if your getting waswas about him being anything more than that remember what Allah says about his noble messenger:
مَّا ٱلْمَسِيحُ ٱبْنُ مَرْيَمَ إِلَّا رَسُولٌۭ قَدْ خَلَتْ مِن قَبْلِهِ ٱلرُّسُلُ وَأُمُّهُۥ صِدِّيقَةٌۭ ۖ كَانَا يَأْكُلَانِ ٱلطَّعَامَ ۗ ٱنظُرْ كَيْفَ نُبَيِّنُ لَهُمُ ٱلْـَٔايَـٰتِ ثُمَّ ٱنظُرْ أَنَّىٰ يُؤْفَكُونَ The Messiah, son of Mary, was not but a messenger; [other] messengers have passed on before him. And his mother was a supporter of truth. They both used to eat food.1 Look how We make clear to them the signs; then look how they are deluded.[5:75]
They were human beings just like us (eating food, working), except Allah chose him over mankind to be a messenger and guide for the children of Israel!
Evil thoughts and whispers that disturb you are clear signs of faith!
It was narrated that Abu Hurayrah (may Allah be pleased with him) said: “Some of the Companions of the Messenger of Allah (peace and blessings of Allah be upon him) came to the Prophet (peace and blessings of Allah be upon him) and said to him, ‘We find in ourselves thoughts that are too terrible to speak of.’ He said, ‘Are you really suffering from that?’ They said, ‘Yes.’ He said, ‘That is a clear sign of faith.’” (Muslim).
I think you need to understand what shirk is and it's forms! Shirk is to associate an equal or a partner to Allah or to perform worship/deeds for other than Allah!
Here's Advice Rasulallah (peace and blessings be upon him) to Abu bakr (may Allah be pleased with him) on how seek refuge from these things!:
Ma’qil ibn Yasar reported: I departed with Abu Bakr to meet the Prophet, peace and blessings be upon him, and the Prophet said, “O Abu Bakr, there is idolatry among you more hidden than the crawling of an ant.” Abu Bakr said, “Is there idolatry other than to make another god alongside Allah?” The Prophet said, “By one in whose hand is my soul, there is idolatry more hidden than the crawling of an ant. Shall I not tell you something to say to rid you of it both minor and major? Say: O Allah, I seek refuge in you that I associate partners with you while I know, and I seek your forgiveness for what I do not know.” Source: al-Adab al-Mufrad 715 Grade: Sahih (authentic) according to Al-Albani عن معقل بن يسار قَالَ انْطَلَقْتُ مَعَ أَبِي بَكْرٍ الصِّدِّيقِ رَضِيَ اللَّهُ عَنْهُ إِلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ يَا أَبَا بَكْرٍ لَلشِّرْكُ فِيكُمْ أَخْفَى مِنْ دَبِيبِ النَّمْلِ فَقَالَ أَبُو بَكْرٍ وَهَلِ الشِّرْكُ إِلا مَنْ جَعَلَ مَعَ اللَّهِ إِلَهًا آخَرَ فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَالَّذِي نَفْسِي بِيَدِهِ لَلشِّرْكُ أَخْفَى مِنْ دَبِيبِ النَّمْلِ أَلا أَدُلُّكَ عَلَى شَيْءٍ إِذَا قُلْتَهُ ذَهَبَ عَنْكَ قَلِيلُهُ وَكَثِيرُهُ قَالَ قُلِ اللَّهُمَّ إِنِّي أَعُوذُ بِكَ أَنْ أُشْرِكَ بِكَ وَأَنَا أَعْلَمُ وَأَسْتَغْفِرُكَ لِمَا لا أَعْلَمُ
Just know at times the companions of the Messenger may Allah be pleased with them had their moments where they would be attacked by Shaytan with disturbing whispers and trust me we are no better.
Just brush it off and continue in seeking refuge in Allah!
It was narrated from Ibn ‘Abbas (may Allah be pleased with them both) that a man came to the Prophet (peace and blessings of Allah be upon him) and said, “I think thoughts to myself, which I would rather be burnt to a cinder than speak of them.” The Prophet (peace and blessings of Allah be upon him) said, “Praise be to Allah, Who has reduced all his [the Shaytan’s] plots to mere whispers.” (Abu Dawood).
وَإِمَّا يَنزَغَنَّكَ مِنَ ٱلشَّيْطَـٰنِ نَزْغٌۭ فَٱسْتَعِذْ بِٱللَّهِ ۖ إِنَّهُۥ هُوَ ٱلسَّمِيعُ ٱلْعَلِيمُ And if there comes to you from Satan an evil suggestion, then seek refuge in Allah. Indeed, He is the Hearing, the Knowing.[41:36]