He may have been trying to "size you up" regarding your taste in rings, etc.
A woman I worked with had been with her boyfriend for two years and she was getting to the point where it was either they were going to get married or she was going to move on. She told him that.
So, one Saturday, they went to all the jewelry stores and she found one that she fell in love with. She was very upset that they left without him buying it. She thought maybe he would go back to get it without her there, but she kept calling the store and even went in. There the rings were. Still in the case.
After 2 weeks of this, she was pretty mad and felt very hurt that he would take her to look at rings and toy with her feelings like that. She was ready to end it. They were invited to a big family wing-ding and she refused to go with him. He finally talked her into it.
Well, in front of family, on both sides, he proposed to her.
WITH A DIFFERENT SET OF RINGS!
She loved the ones he got her so much more than the ones she'd had her heart set on and was so thrilled she didn't get what she'd been hoping for.
He knew what he was doing....he just wanted to get an idea of what she really liked and he bought the rings at a store they hadn't even been in. She was totally, very happily surprised. The rings are gorgeous! They had a fabulous wedding 6 months later.
My point is, sometimes when men seem like they are being lame, they really aren't.
My mom got so mad at my step-dad one year because she totally thought he bought her absolutely nothing for Christmas. I played along because he and I had gone to a jewelry store and picked out a beautiful ring for her. He let her get good and mad and then sprung it on her just about the time she was ready to shove the turkey where the sun don't shine.
Maybe it's just me, but anytime my husband or significant other offered to take me into a jewelry store....I went.
If you're upset and withdrawn, he likely knows something's up. You might as well just tell him how you feel and get it off your chest. You've been together 4 years, so if you can't talk to him about this there are bigger problems than a ring.
Just my opinion.
Best wishes.