Cheating? (Long read)

SO my boyfriend and I went out tonight and i read his phone while he ran into the gas station. I noticed some texts he had with a girl from about a month ago. The girl is one of his close friends and the guy shes dating is my boyfriends good friend also ( im not really friends with them). Anyways, my boyfriend seemed to be flirting with her. I few days before she had been in a terrible car accident and was still in the hospital while they were texting. That night he texted "i don't know what i would do without you. I'm glad you're okay" AND then they got to talking and he was saying that if her and her boyfriend , WHO IS MY BOYFRIENDS FRIEND, didn't work out then he wanted to try with her? And she didnt reply. So he continued to text her another 2 times. Saying He was serious and asking if she was still there. The rest of the night after i saw these texts i was just a huge bitch to him and then i finally decided to confront him even though i had no desire to argue. And he swore he was "joking" and that him and the girl were really close friends and they had always been that way. I also read his facebook messages of where he personally messaged a girl ( instead of just writing on her wall like a normal person) and said "happy belated birthday😊". When i confronted him about that he said he didnt want to post it on her wall bc he didnt want me to see it and get mad?? Am i overreacting or is this cheating? I'm so over feeling this way and i honestly dont know how much more i can take from him.