tried something new last night

ok so my girlfriend and i are both trans guys but we have this kinda open thing going on with other people and its complicated af im not really into cheating or anything but when i told her about someone else she was cool with it. anyway long story short me and this other girl were flirting online for days and last night we decided to finally give it a shot. i mean like we talked all the way through about how weird it would feel and stuff but once we got started there was no turning back. everything just kept getting hotter and hotter. i have never felt so alive and free before in my life, you know? but afterwards i was really conflicted cuz i love my girlfriend a lot and even though she said she wanted me to be happy shes still been texting me upset since then and i dont wanna hurt her. plus im just kinda worried i made things way worse by not telling her what it would actually feel like with someone else. so is this totally fucked up or am i being too hard on myself? do you think the whole thing was wrong even if we agreed to all of it? im scared about how to move forward from here.