Should I continue with him and eventually marrying him?

Recently, I get to know my bf's mailbox pword, so one day, i decided to go in and check if he read the email i sent him alrdy. Since he has a bad internet connection, i wan to confirm if he knows I was waiting for him online. But yes, he hasn't read them, meaning the internet connection breaks down and he couldn't come online. So out of curiousity, i went to see his other emails. To my amazed, I found that he wrote to gers, about wanting to know them and if able to have feelings for each other, then can enhance the relationship! I was totally shocked, coz he used tat to get to know me in the 1st place, after that then we get together. Nw, i feel so sad, tt it seems that he betray me. Do u think i shld 4give him if he asked me to 4give him and eventually marry him at the end of this year? His mother says that his alone overseas( studying), so maybe he's just being lonely and do stupid stuff. But y? when a person tells u how much he loves u and cannot do without u wil do this kind of things?pls help!