Of course this a big shock. Because you are a nice, normal, decent person (with normal flaws, like the rest of us), who loves her OH and wants to be nice to him, it's hard to understand or accept what he's doing, and to come to terms with it,because you presume others will be normal and decent too. But keep on remembering that the keys to understanding if something is abuse are:
Does he act like this to others, or does he choose not to? If yes, then it's abuse, because he is then choosing to do that to you.
Would you do and say the same/similar things to him, or anyone else, in the same circumstances? Is this behaviour how the majority of couple act towards each other? If no, then it is abuse. Depression, stress, whatever, are not reasons for abusiveness. Abusiveness is the reason for abusiveness.
Does this behaviour make you feel sad, worried, guilty, scared (not nec. physically), like you're somehow to blame, even though you know you're not? Do you find yourself reassuring him, trying but failing to placate him, to make him 'see the light'? Are you scared to do what you want, even though you know it's something completely normal and reasonable (and even if you still go ahead and do it)? Do you find yourself altering your actions, behaviour, words, choices, plans, lifestyle, etc., so as to try to minimise or stop him getting angry, hurtful, rude, negative, suspicious, and so on? If yes, this is not normal and you are being abused.
Does he ever accept genuinely that he has behaved or spoken horribly or unreasonably to you? Does he take responsibility for his own actions? Does he apologise - and if he does, is it a proper apology, eg no "I'm sorry
I said X, BUT... ", or trying to find an excuse as to why it wasn't his fault? If so, this is not genuine remorse or understanding of what he's done wrong, it's just him begrudgingly doing what he knows he's expected to do to shut you up, and is a classic abuse sign).
There's more, but these are the main ones to keep thinking about.
All abusers are nice, when things are going their way, and when it suits them to be. They can even be wonderful, and amazing, but this is the flipside of their unbalanced, damaging and damaged side, and the odd glimmer of wonderfulness does not make up for abuse, ever. Abusers also tend to go for feisty women, which is why so many women who are abused have a hard time seeing themselves as someone who has been abused.