concerning... a lot of things;

He won’t hug Clara out of reluctance surrounding just her. This is nothing about being a hugging person or not. The common denominator in the hugging situation is Clara, not the physical contact.

While, obviously, he’s less affectionate in manner than previously, a lot of it does come down to the circumstances regarding his regeneration. Before he left London Vastra quietly voiced her concerns, prompting the ‘I’m not your boyfriend’ conversation.

After the attention from women The Doctor has been used to for the past few hundred years, it’s understandably been some knock to his usual sense of confidence to become older, not the younger and more typically handsome incarnations prior. He particularly doesn’t like this new body because he thinks others disapprove of it, or it’s not the same. That he looks cross, unfriendly, bitter.

The change in Clara’s attitude recently has certainly highlighted this, and it’s become clear to him now that he’s more of a grumpy old man in her life rather than the alien but equal he was before. Her supposedly uncaring nature toward large differences in his behaviour and the need to shut down what he’s saying as something 'odd’ are causing him to think she just doesn’t care any more.

He’s not going backward and forward in time any more just for fun trips. Sure, he’s looking at strange phenomena and theorising and working out the universe, as ever, but he’s doing most of it from the TARDIS. He’s living in there more, we’re seeing more of him pottering about the console room. He’s taking his time in working out who he is. His outfit is still changing and he’s still tasting different foods all over again.

This time he’s unsure of everything. He can’t come up with plans any more until the last minute. He hasn’t the foggiest what is going on sometimes. These past few glimpses into life in the TARDIS are starting to look like The Doctor would rather stay at what’s technically home. Look into his hobbies and work things out in the pursuit of knowledge and drink awful filter coffee and eat porridge and search out that jumper he never wore.
 
The Doctor is getting old. I think his memories might truly be failing him sometimes. This is made all the worse by Clara apparently disapproving of all of it. It’s making him uncomfortable. He seemed to hardly be at ease with her being affectionate toward him as his previous self, and now it’s become even worse.