So if you are convinced of what you pretended: then normally after the 3rd talaq you should refuse him, separate and leave him -if possible- and try to seekprove that talaq happened (if you have at least 2 witnesses) or khula' as he became mahrama foreigner for you as he is -from a shari'a point of view- no more your husband, so he shouldn't see you uncovered neither have intercourse or any kind of relationship which is haram with a mahramforeign man!
- In this fatwa a man gave 3 times talaq to his wife after 30 years of marriage, while he is denying and he refused giving her talaq in front of the mufti/court ... again the scholars answered that the woman should flee from her (former) husband if she can and should act with him as with a mahramforeign man if she has no doubt about being given 3 times talaq and he also explained that it's not necessary to have witnesses (or court etc.) for the talaq to be legal as the Verse (65:2) is explaining the matter which needs witnesses:
- In this fatwa a man is asking about his wife who pretends ha has given her 3 times talaq while he only admits 2 of them. Again the scholars said the saying is what the husband said unless she had 2 upright witnesses. Imam Ahmad even refused the option of two female and one male witnesses! Again if the woman is sure to have heard the talaq 3 times she should flee -if she can- and refuse having intercourse etc.
He also added that some scholars said if the woman had one witness the man should make an oath, if he refused then she has to make an oath and would be divorced based on this hadith from Sunan ibn Majah (which is qualified as da'if) which is also in Sunan a-Daraqutni! Ibn a--Qayyim said that all scholars and the four sunni madhabs accepted the paper of ibn 'Amr ibn Shoaiyb from his father from his grandfather (the narrators of the hadith) except a few like ibn Hazm and abu Hatim al-Busty...! Imam Malik instead accepted -in his Mudawanaal-Mudawana- two upright female witnesses based on this hadith! So if the man accepted to make an oath this would invalidate the one witness if he rejected that would support the claim of the woman/wife!