All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
We explained previously the conditions for the validity of marriage in Islam in Fatwa 83629. Among the most important conditions are the presence of the bride's Wali (legal guardian) and witnesses. If the bride has no Muslim Wali and another Muslim man, whom people acknowledge his entitlement to handle Muslims' affairs in the community, acted as her Wali in concluding the marriage contract, then the marriage is valid. It is enough to have two Muslim witnesses present at the marriage contract session even if they were not asked to be witnesses to the contract. If more than two Muslims are present, then the condition of having witnesses is fulfilled with even more certainty.
There is no harm in a non-Muslim attending a Muslim's marriage contract session and this does not affect the validity of the marriage; however, he is not a valid witness to the contract.
What your husband says about you having to say that you accept him three times is incorrect. Not having children is the Decree of Allaah and it is not necessarily related to the validity or invalidity of the marriage contract. There are many couples whose marriage is valid who are unable to have children.
Hence, if your marriage was conducted with the above-mentioned conditions met, then it is valid. In this case, you are advised to disregard any devilish whisperings and ill thoughts suggesting otherwise. Even if we assumed that any of the conditions was not fulfilled, then you can simply renew the marriage contract.
We do not know what you exactly mean by "correct ceremony". The Sunnah consists of preparing a wedding banquet and inviting people without extravagance and ostentation. It is also recommended to announce the marriage by means of permissible singing; but beware of allowing impermissible intermixing between men and women, indecent singing and music. For more benefit, please refer to Fatwa 114861.
Allaah Knows best.