There's some reason in particular why he's being rude out of nowhere?

(sorry for the english)

My boyfriend 42M is away from me 29F.

Today we did a video chat to celebrate Valentine's Day. It was all good, i told him i'm going to visit him soon, told the news and everything. He's away and we can't communicate much.

At some point, I joke with him: "How's your other girlfriend treating you while i'm away?" Sometimes I do this because I'm a very insecure girl lol unfortunately...

He laugh, and then, out of nowhere, he started saying/remember that I didn't do something that he asked for a while ago. He asked me to buy something and I didn't. He was like: "I'm fine, but i really wanted that. I dont like to be saying many times. I hate to do that and i really wanted".

I work every day. I am busy and i'm saving money to be with him. Buying this thing it's not a problem, but i forgot. And I didn't think it was important for him. I said sorry.

I'm just really sad that he would be pointing that and making me feel sad at Valetine's Day. Like, things like this make me doubt so much.

Why do this and act like that today? Is there some reason? Why look for a fight out of nowhere?

Thank you for advices and patience!