Why did my husband change after we got married?

A lady that my husband works with kept telling my husband that as soon as we got married I would change and stop doing things for him and eventually take his house, savings and property away from him and that my behavior would change and that I would turn into a different person. She is a very unhappy and negative person and my husband and I understand that. We lived together for 2.5 years before we got married and life was perfect. He finally trusted and loved me enough to ask me to marry him. Then HE did a lot of changing. It started out slow and now it is to the point that I feel more like his friend or roommate than I feel like his wife. We are great friends and have great love for each other but he is so different as far as a husband. He used to show me affection and say nice and romantic things to me and it was wonderful. I know time, energy and so many other things get in the way and things will mellow after a while so I expected some changes. Both of us are on our 3rd marriage. We haven't had regular sex since the week before we got married. He seems more interested in younger girls on the computer than he does in me. Girls that look like I used to 20 years ago. It is not a lot but it is not me either. I am starting to feel like he is cheating on me. He recently stopped drinking and he partly blames lack of interest on that but I don't think that has anything to do with it because he has quit drinking before and there was no problem with sex then and he lost interest way before he stopped drinking. We both know that he has hit midlife crisis. He is 51 and I am 44. I'm sure this has something to do with how long the lack of sex thing has lasted but he shows no affection anymore which he used to but it has slowly dwindled off to nothing. Now he is usually grouchy with me when we are home together. It feels like he loves me but he is tired of me more. I try to give him his space and alone time but it never seems to help. We usually have different days off and we used to run our separate errands while the other one was at work so we could spend time together. Now he waits until I get home and then leaves to run his errands. We used to have great communication and now I can't bring anything up because it upsets him. He WON'T talk about anything especially if the TV is on. I have to wait until he pauses the TV or he gets irritated with me. If I do say something I have to repeat myself because he doesn't pay attention to me. I love my husband and he loves me but how long is this going to last? He doesn't even notice or say thank you when I clean the house or even a room. He used to always say thank you or the kitchen looks nice or whatever. Now he doesn't even notice. When I work on his days off he would always call or text me when he woke up to say HI as I still do for him. Now he doesn't even do that anymore. We have no kids at home so that is not an issue. I am 5'5" and 140 pounds with long dark hair just like he likes and I feel that I am very pretty. I brush my teeth and hair, I keep myself clean and as fit as I can at my age. I see the way he looks at me when he thinks I am not looking so I know he likes the way I look. I contribute financially to the house and all of our bills are always paid. I don't know what to do and I don't know how long this is supposed to last. We haven't had sex in 4 months. I have no urges to go anywhere else and he knows it so that is good. He keeps telling me to wait and he will eventually get over it. What do I do to ease everything until this "phase" is over?