all this happened over four months? After three years with the first boyfriend? That's probably not long enough to get your emotions straight. In fact it certainly isn't, otherwise you wouldn't have posted this. Time is a great healaer; you need time to sit back, think, feel, consider what you want and how much each of these guys provided it for you - and also the things they may not be providing for you.
Best thing, I imagine, would be to tell the new guy the truth: you've recently had other relationships, you are still getting over them; you like him but you feel you mustn't rush. If he's genuine he will wait - nobody would push a relationship too hard if he knew it was hurting the other person.
In particular, regular routine things, like Christmas, will always bring back memories of the way you spent previous ones. So I wouldn't be making any big decisions until you've got that out of the way at the very least.