It's either he is refusing to even acknowledge it at all, or trying hard to hold back the things he's feeling, these could be the reasons why:
1. He fears you won’t reciprocate
If it’s at the early stage where you are only just befriending each other, a man could be forming hard guy, clamping down on his feelings for you in an attempt to a get a little more clarity. He’ll first want to be sure that you like him back or that there is, at least, the possibility that you can be convinced with a little more wooing and show of affection.
Until he gets a clear green light or feels that the odds of getting you favour him, he may continue to keep a lid on how he truly feels.
ALSO READ:All the sad realities of dating a man who can't express his emotions
2. He does not want to be lame
There’s a thing with certain women [and men] which causes them to associate an openness about emotions with ‘being lame.’ No guy wants to appear lame. He always wants to stay in charge of the situation, he wants to be ahead of the curve, and to be absolutely sure that every emotional expression is appreciated and increases his rating with you.
It is expected that men may be masculine, to not be a sissy or to not be effeminate. Sadly, processing and expressing emotions has been covered under this 'effeminate' blanket.
3. You could use it against him
The decision to hold back on those feelings could also be influenced by a desire to not become vulnerable and concede too much power to you.
There is a belief among men that when a woman does not know or is unsure of your love for her, she’ll be humble and act right towards you. The moment she knows, however, the power dynamic changes. It is believed that from that moment, she may begin to exploit you, either financially, emotionally or in other ways.
So when he’s forming hard guy, it could be his way of preventing this from happening.