IS THIS CHEATING???

Riley
-SO this was the summer of 2015 so about July/August 2015 
-At 11am My boyfriend told me he was going fishing and told me who would be there(3 of his friends and a girl)
-We made plans for that night and agreed that he would pick me up at 5:30 and we would go to his house and eat. Then he said bye and I let him go have fun.
-I talked to him about 3:00 and said "you're still picking me up later right?" To confirm our plans. He replied yes. And we didn't talk anymore.
-Well 5:30 came and I had heard nothing from him since 3.
-2 hours later, I get a text from him saying he's on his way, "he forgot" (I refused to go with him for obvious reasons of forgetting me)  But his story kept changing and he started saying his phone was dead or he didn't have signal.
-The next day, I asked him why/how he forgot me(his girlfriend of almost a year at that time)
-He said his phone was dead and I said no, because you texted me.
He said he didn't have signal and I said that's a lie because the girl had pics of him on snapchat..
And he was like "you wanna know the real reason I forgot?" And I was like obviously. And he said "well SHE got there and I was having so much fun and she was funny and I didn't wanna leave when she got there."
-So this still hurt b/c he lied but I could understand if he was having fun with his friends..
HERES THE BIG PART :
•Then I found messages in his phone on his snapchat and stuff that was telling the girl how he loved her and that he wanted to break up with me for her and he was going to make it to a year with me and break up because we aren't doing too good anyway. And that  he wanted to date her and he loved spending time alone with her. 
•honestly I think even if he had so many messages like this to her and he didn't want me to see and lied about its cheating.. What do y'all think?

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