Hi, I just wanted to let you know, you aren't alone. My husband is/was very similar. First thing home he would disappear into his office and barely come out. I, too, was very frustrated and disappointed. The hardest part is that I could understand if he was doing something important (paying bills, etc) but when he just is randomly surfing the Internet while I'm cooking and entertaining our son, it would drive me crazy.
For me, there were a couple of things going on. First, the honest truth is that little kids are wearing to him. He loves our son, but he can only handle small doses. As our son gets older, he is enjoying him more and more. Secondly, he did agree to go see a psychiatrist and that has been amazing. I personally can't stand taking medicine, but, wow, did getting on some anti-depressants make a huge difference. I know not every man who "hides" is depressed, but sometimes there truly is a chemical/medical issue going on. If your husband is open to at least exploring that option, it really has made a huge difference! I used to cry all the time, thinking "is this really my life," but not anymore. Now my husband is out of his office and interacting with us and living again. He is exercising, planted us a garden, and taking my son places on the weekends when I need to work.
He still needs some time to himself to unwind (he is introverted), but if it gets too much, he is much more open to hearing it. I hope something changes for you soon as I know it can be very difficult. And, like some others said, find something for you that allows you to get away sometimes. Good luck.