Hello and thanks for question.
You do not have to wait 2 years. You can choose to base your divorce petition either on your husband's adultery - until you get the decree absolute, if he sleeps with another woman, he's committed adultery - or on his behaviour generally.
However, adultery can be tricky if he's not prepared to admit to it on the divorce papers as it's too expensive to prove it, so you or your solicitor needs to make sure that he agrees to admit to the adultery before the petiton is prepared and sent to court. If he will admit to the adultery, the petition can then be very brief, which is more amicable and easier for everyone.
In England & Wales, the co-respondent does not need to be named, and it's considered good practice not to name them, but I don't know if that's the case in Northern Ireland.
In a behaviour petition, the petitioner has to set out incidents of bad behaviour, which is not pleasant for the respondent to read, and so can make the divorce process less amicable, and negotiating about property & finance associated with the divorce more difficult.
I hope this helps and I wish you the best of luck.
Thanks and best wishes...