Please help me with this issue :(

Recently I found that my boyfriend had been talking to this girl who he met on a tour. He never once mentioned about her and he usually talk about his friends and who he meets but not this chick.

I randomly found out by just touching his apple watch and the old notification appeared. “wanna talk?” with a cute cate face emoji. He knew that I saw it but he never talk about until I started talking.

One day when we were hanging out (this was before the pandemic shit) i borrowed his phone to see if he delete the convo with that chick.

Turns out he did not. So I read the couple of their last messages quoting him to the chick “I am sorry if i made you taken wrong signal about our relationship ... then smth smth ... about not the right relationship” then she said smth i cannot remember. He did not reply her message . Then after that is her “wanna talk?” message. Again he didnt answer.

I asked him about who this person?

He was like “oh its nothing”,

then I said “if its nothing how come you guys talking about the stage of your relationship and why you gave a stranger your phone number when you used to tell me not to?”

He then said: “its nothing I hung out with her like twice during the trip and thats it”. then he stopped. so I never mention about the story again.

But it bugs my mind!!! still to this day (its been at least 2 months)!! Please tell me if i am over reacting and crazy... The following are questions in my head..

- Did he stop talking to the chick just because I saw the message? or maybe they have moved to another platform (fb or insta) to talk? Did he actually stop talking because he feels guilty?

- Why in the explaining message from him to the chick he didnt mention that he has a girlfriend? it would clear everything up for him so quickly but he didn’t...

- Why didnt he go into details when i talked about it? what means by nothing if it was nothing why they talk about the signal, the relationship? was he cheating on me?

- The thing is that Him and I are on a break in the relationship because he said he needs time alone to think about his career path (he just graduated). He once told me long long long long so long ago that he might have to go to another the city to pursue his dream job. However it now happens to be that chick’s home city too. What if during our break he had already moved to the city? oh fuck...

- I don’t get our break though, the pandemic already makes us not being able to hangout, we don’t talk evn that much on texting (like adequate not obsessive - I normally dont even text that much at night time and during day time he normally sleeps) and we dont even video call... so wth... why does he need time alone..? arghhhh IDK

Please tell me what you think... what should I do???????? btw we have been dating for over 1.5 years.. we had multiple fights during the beginning of the relationship, he said he was tired and wanted a break then he quickly decide not to... but this time it’s different...

P/s: sorry for the long post but thank you for reading it :)