Will my husband regret not putting any effort into our marriage?

I have been with my husband 5 years, married for two. Generally we have had a great reationship, the usual bickering and arguing but nothing major. We have a good life, are financially secure and have great friends. Things changed at the beginning of the year when beause of other committments we stopped seeing each other so much - it was mainly due to my work as I had a lot of overtime, he works shifts and only has one weekend off in four. Our conversations seemed mainly to be about the house and mundane stuff like that. I felt the intimacy was going a little and decided to put in some effort to spend quality time together, but he just didn't seem interested. I kept trying but then in April when we were away for a weekend I found messages on his phone to a work colleague - one telling her he missed her and the othe r saying that he'd been trying to call her from a phone box. I was devastated and confronted him about them. He was adamant they were only texting and talking, and it started because he felt we had lost our 'spark'. After a couple of weeks thinking I decided I did not want to throw away my marriage if we could get it back on track and I really wanted to try. But he decided he didn't want to and said he had decided there might be someone better out there for him. He's stuck to that since and I'm now in the process of buying a house and moving out. I feel competely shellshocked by it all, and don't understand how he can just throw away a marriage like it was nothing and didn't require any effort. He has always had a very easy life and had everything provided for him - I feel he just thinks that if a relationship takes effort it can't be right. But surely a bit of effort is going to be needed after 5 years? I feel very ashamed that we have split up so early on, but know that I can't force him to be committed. I've done my best to just get on with my life, but now other guys are showing an interest in me he doesn't like that either! Should I be patient and hope that he's going to regret what he's done? Or am I better off putting him behind me because I would never be able to rely on him when things do get hard? I change from day to day and really don't know what to do for the best.