Is it stupid to be upset?

I've been feeling really down and depressed since Thursday. I missed out on a short road trip with my bf because my gf had invited me to a family function because bf asked if i wanted to go with him. That would have been fine if my gf and her mom didn't decide to leave a day early, which meant I couldn't go (i can't drive, and the function is hours away with no public transport between). so I've been at home alone, with absolutely nothing to do except think. I'd gotten over it a bit, except when i asked her what she was doing today when she got back, she said she's going to be hanging out with a girl she has a massive crush on, and I've been insanely jealous of this girl lately (we are open + poly so i have no issues with her dating other people, it's just this one girl + my own issue, not hers). bf won't be home until late so I'm just stuck here. I'm with my family but i feel so alone. even my mom isn't here this weekend. i just want to feel like I'm important. i was hoping + looking forward to hanging out with my gf. she says shes trying to get her shift for tomorrow covered so we can be together all day but part of me wants to tell her not to bother bc she needs the money + I'm not really happy right now and i don't want to be like this around her, especially when her actions are what caused my brain to spiral.

This just feels like such a stupid, trivial thing to be upset about. but i could have done other things this weekend. there were things i could have done but said no to bc i had plans, only for the plans to suddenly not include me last minute.