My partner hides their phone from me

Recently, I've noticed my partner [29M] has been very secretive with his phone, even leaving the room to take calls. We're both 28F and usually shared everything—now, there's this distance. He says it's just work stress, but it's hard not to worry. Should I confront him or give it time? Any advice? #BreakTheSilence #TrustIssues #RelationshipWoes