How to tell if a shy guy likes you back?

I’ve been liking this guy for 10 months. We’re around 19. We started off as flatmates living in the same uni hall. He’s very shy and introverted (ISTJ), doesn’t talk much, said he’s never had a crush on anyone (aromantic?). Had basically no female friend, never dated. We became friends in the last few months and have a common friend group. This year we don’t live together anymore (moved into private accommodations) but still keep in touch with friend group. We’ve gotten closer (now he would respond to my messages in group chats which he’d never do before, would congratulate me when I’ve made an achievement, definitely interacts with me more than other girls) and hang out with the others about once a week. Whenever we talk, he’d always look down at his phone (doesn’t maintain eye contact) even tho he’s normally a nice and polite guy and I don't know if it’s my illusion but i feel like sometimes he’s staring at me when i’m not looking - when i look back he looks away.

Due to some reasons, I’m not supposed to like him (us starting a relationship is forbidden), and he knows it.

About 2 weeks ago, at a party I was getting a bit drunk and emotional. I was sitting on the staircase alone in the dark, he came along and stood awkwardly next to me for a bit in silence, asking if I wanted to go down to join other people. I said “You know, I kept on catching feelings when I first met you”. He immediately looked down and shook his head, i then said “but it’s fine now”. Then he diverted the topic to something else. That night when i was leaving he walked me to the door and waved at me. The next day (a bit stupid) he sent me a gift on Pokémon go with a sticker. he rarely sends gifts in the first place because he hardly goes onto the game anymore, and NEVER adds stickers to them. After that night he started being more caring and nice to me.

Has he also been having a crush back, or is he only acting nice because i kinda confessed? Is he only being nice as a friend?
How to tell if a shy guy likes you back?
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