How would you feel if your boyfriend did this ladies? guys what does it mean when a guy does this?

Okay so I recently started going out with this guy and I REALLY like him. The chemistry is overwhelming. But right now I'm not feeling too sure. We were talking about seeing each other tonight all day today. A few minutes ago he text me saying he will be leaving in 35 minutes, about 20 minutes later he says he has a lot to do for the next few days and he can't make it tonight. That seems really shady to me. What bf does that? Could he be talking to someone else? I looked through his phone and saw a conversation he had with a girl to hang out, but it was dated before we started going out. Could he be meeting up with her? Maybe I am just over thinking it. He hasn't given me a reason not to trust him yet