my LDR bf of almost 3 years and I are going thru a phase

So, hi! I'm new here actually. Just found this forum in IG and it kind of stuck well as I do need something to let out din. For a short background, my bf and I are college students. My bf is still on his first year of school. He's doing well in school and to cut it short, there's this new seniors that he's become really close to these past few weeks. But it really just concentrates to one senior girl that I kind of not like. hehe. We've talked about this already and he does assure me but recently things have been hard. He spends most time with this "ate" after school; for tambay and coffee or study or gym and sometimes out night at the bar, welp with some other senior friends too. But this ate is relatively close. He says there is this platonic "click" with her and it eats me. We do share our social media account password with each other (my bf's idea). I can see them getting really close in chats and they just always invites each other out. and right now, they are even ninong and ninang to this specific baby just because they shared a drink with the mom. And just last monday, they bought this gift togther and my bf just informed the morning he went with her despite knowing the plan days before. So yk, :(( . He said he thought he told me na. So, basically, they bond thru vices: smoke, drink. My heart sinks and I basically told him its okay to go make his connections for future help, also since I trust him but i think i overstated it. And he's moving past the "okay" boundary. One night he shared something to me and said that they talked over a drink (when i was out with my friends and we had a small misunderstanding the morning of that day). he did not even told me he was drinking with her and only told me when i asked for an update. what they talked about was that the ate thought my bf was into her. and my bf also thought she was into him but they both dismissed it so he felt assured. he told me that and saying i have no reasons for distrust. But just knowing that means that he's over satying in her attention, time and everything. He's making her feel more than just "platonic". He said he gets what I'm saying but he thinks he's doing nothing wrong. HHHAHAH i didnt know its this long now. we did talk already and he said he's gonna limit his time and attention woth this ate but its difficult ofc because he is his working student rn. so, they still see each other as often but i did tell him im removing his accounts on my gadgets so i dont go craycray checking his dms because of this anxiety. and I'm focusing more on my leisure time and decided to spend more time outside in parks or coffee shops and read my bedridden books. just wanted to rant 😆 so happy this platform exists!