Should I or should I not text an ex to apologise?

Wow you were rude. You got confused over his simple happy holidays message so he will definetly get confused over your apology. Seeing as you dont want to get back with him i suggest you dont apologise. This will only bring back all the bad memories for him. It has been a few months gone now and i think you should just leave it. The time to apologise and say what you needed to say has gone and you will only make things work. You are going to have to deal with the consequences of your behaviour and learn from this. This was a life lesson for you and now you know that in future, it is important to handle the break up carefully. Learn and move on.