One or two people have taken issue with me over my posts on this thread, so I have taken the time to read the entire thing over again, read other comments, but paying particular attention to the OP's posts.
The OP says she doesn't realise she's doing it, and as far as she is aware, doesn't do it to anyone else. Some people are saying that it is abusive behaviour.
It has belatedly occurred to me (and since this is Mumsnet, I'm quite surprised that nobody else at all has stopped to consider), whether there may be other things at play here.
Firstly, on many threads when someone's behaviour is odd like this, there will often be posts suggesting that the person may be neurodiverse in some way. No-one has said anything like that on this thread, yet it could be a reason for someone to unwittingly repeat a behaviour over and over again without knowing they are doing it, and therefore be unable to stop.
Secondly, it is well known that abusers often accuse their victims of being abusive. The OP doesn't know she is asking 'why' all the time, and as far as she is aware, doesn't do it to anyone else. So there is in fact the possibility that her DP is gaslighting her by telling her she is doing this when in fact she is not, and he is then accusing her of emotional abuse.
Thirdly, from the examples shown, they could be perfectly reasonable questions as part of a normal conversation, if for instance he would normally always have loads of extra sauce and inexplicably turns it down. Or if they are very short of money and she is asking why he's bought another pair of shoes when she knows he has 17 perfectly good pairs already. Someone who thinks they are King of the Castle might be infuriated that their subordinate partner has dared to question them in any way.
Finally, the overwhelming majority of the early posters on the thread said they didn't think it was abusive, and the thread suddenly changed tone with a pile-on of people having a go at the OP and others joining in, which all too regularly happens to threads on MN. Disappointing.