Is he cheating ?

Me and fiancé been together for 3 years wev has our rough patches and that he proposed to me last month and was so excited to plan a wedding he couldn’t stop talking about it! But lately he’s stopped talking about it , I mean he’s been really nice , which yeah we want but he’s been “ too “ nice it’s not normally his behaviour if you get me ? He’s one of those guys who dosnt always want to cuddle and like his space and that which Iv always respected but lately he’s been quite clingy , anyway to the point tonight he has his friend over I was in bed but decided to go down stairs for something to drink his phone was on the side so I just clicked on it to see the time and he ran over so quick and started shouting at me “ don’t be snooping through my phone that’s my privacy “ even though I was only checking the time ! He then went in to say I always ruin his fun with his friends and that I’m always paranoid when honestly I’m not ! I’ve trusted him 100% till this very moment it seemed out of character , he always goes in my phone , he’s never had a problem with me in his , I don’t just take it and snoop I would never but if I wanted to watch a video or play a game I would ask him ( if my phone is dead or on charge “ and he’s never once had a problem , I wasn’t really suspicious until now what does everyone else say ? He hasn’t even come up stairs to Apologise and it’s been over an hour !