Telling the father????????????

I am pregnant with twins the father and i used to date in college and he was my first love.At the time when we met up again i was seperated from my hubby and was in the process of divorcing and he was seperated from his wife and mother of his daughter.We went out had a few drinks since he was a lawyer we discussed my divorce proceedings and well had one too many drinks resulting in my pregnancy.My ex.bf is considering going back to his wife?Should i tell him now or later?