Guy problems..=/ please help me out.?

So theres this guy that i dated for about 1 month, everything was going well untill one day he went to go pick me up at school but he was different. I asked him what the problem was and he said nothing. Later that day he left my house and said I love you. This guy always messaged me at night to say goodnight but not tonight? So I wait till the next day and send him a message like at 3:00 pm saying "hey whats wrong? and no response. I started getting worried it was now 9:00pm i send him another message saying "Are you okey? i'm really worried about you??" he now replys and says" Im sorry, it's just that something really weird happened to me today, I saw my ex girlfriend and I realized that i still like her, im sorry but i think i need some time to see what i really want." OMG totally unexpected right..Well the next day i asked him if he had any contact with her and he said no and i was like ok. On the 3rd day after we werent together, i went to the mall and i saw him there with his ex girlfriend. =O so he did talk to her he just said no?? Well now it's been like 1 month since we broke up and he has been saying sorry to me since the day i saw him, he says that he's really sorry, that he didnt feel the same with her as he did with me. that she didnt make him as happy as i did. I do really still like this guy. What are yalls opiniones?? Should i or should i not date him again?? oh i'm 17 and he's 21??