<human>: It's currently 04:45 and I'm lying awake at my boyfriend's, unable to sleep because I looked through his phone and saw that he's been texting, and contacting through various other social medias that he does not use with me, another girl. 

We are childhood sweethearts but have been together officially for 2 years, we were each other's first relationship, first kiss, first love, first everything. My mum loves him like a son and his parents love me. Initially, he pursued me, and because of the age gap I was reluctant. But he won me over and has been great ever since. 

Recently, he went away on a holiday with friends and became very close to a (single) younger girl he had only known as an acquaintance before. Since he got back, he's been texting her fairly lengthy messages non stop (and more than he texts me). Some of the messages were inappropriate, as well as him suggesting that they meet up. You can tell that his feelings aren't returned but that he's clearly pursuing her. Reading the messages literally made me feel sick. I know that it was wrong for me to invade his privacy like that, but a mutual friend of ours had warned me something might be going on and I wanted to prove them (and myself) wrong. 

When he was on the holiday and I heard about his male friends teasing him about liking her, I asked him if it was true. He sent a long response telling me that he liked her but assuring me that it was just as "one of the lads". I suffer from anxiety which doesn't help but I feel like he's been lying to me. 

I'm not sure what to do. I think I'll get a taxi home in the morning and figure out what to say to him and speak to him later. I'm not sure if I should break up or not. It would destroy both of us but I have a feeling he would move on quicker. Am I overreacting? Or would I be dodging a bullet?

I don't think he would ever physically cheat on me but I just don't know, but he already seems to be emotionally.

Can you condense the text into a few key points?
<bot>: boyfriend of 2 years is interested in another girl. Unsure if I should break up or if it would be over reacting.