How do I get my boyfriend to understand..

So, this morning I needed to get some errands done before class but when I got in my car I remembered I left my wallet in my boyfriend's car last night. I called him to ask if I could pick it up and he said he would drop it off no problem in 20 min. Over 30 min goes by, I figure he's running a little late as usual. I get a text that he'll be there in 10 min. Another 25 min goes by. I'm used to him being on the late side so it's whatever. He calls me and says he just got out of the shower. I'm pissed and I let him know it's not okay to do that. I could've come picked it up in 15 min, or he could've let me know he wasn't coming so I could shower before I did my errands or at least not sit and wait around for him. He thinks me getting mad is funny but I feel like he has a hard time understanding that it's not cool to do something like that. He has no respect of other people's time! But if I'm late by 5 min he gets annoyed sometimes... I love him to death but he irritates the shit out of me! Anyone else have this problem?