I just need a little advise

Hello,

I need advice or just someone to talk to. I’m dating a new guy (8months) and everything was great and all until a mutual friend told me he was talking to another girl. I went through all his messages and he did throw in a few flirting in their conversations. I chose to move past it and continue out relationship. But it eats at me that he did this. He claims he loves me more than anything but I swear I don’t know if he’s telling the truth. How do I know what we have is worth it?