I am pleasantly surprised that my estranged partner has started being real?

about his feelings. After 4 months apart, he is now telling me that he loves me and misses me so much. He says he's sorry for being selfish and not considering my feelings. He's just been thinking about himself and all of the things that stress him out. He wants to change this and start putting me first again. He thinks he's sorted out his problems and is ready to give our relationship his full attention. He wants to make me happy. I should be happy about this. His lack of communication about his true feelings was part of the reason we separated. Now that he's actually telling me the things I want to hear, am I being silly to question it? Should I finally believe what he's saying and go for the chance that he's changed? We were together for almost 4 years.