I didn't see a related or similar question, but if you can find one, please link it and I'll close this.
I had little experience in high school and college and learned some of my skills later. My first two serious girlfriends were in my twenties and they both cheated. From this I realized I didn't enjoy serious relationships, so I've avoided them. I have always been honest about this with people I date: "I'm just having fun and don't want this to ever get serious." This is my way of making it clear so that if the person wants "something more" - like marriage - they can move on faster. I just want to have fun - hang out, party, etc with the expectation that we'll be together for a few months with no intention of it leading to cohabitation or marriage.
I live in the US and am about to be 30.
My latest three dating experiences have ended with the other person upset about the relationship not becoming more serious, even though I made it clear that I would never get serious with the person.
Me (initially): I don't do serious relationship; no boyfriend/girlfriend - just hanging out and having fun together.
Her (initially): Great, I'm not looking for anything serious either.
Her (later): So we've been seeing each other for a few months ... [or some derivative that usually starts a conversation about where is this going, even though we both agreed initially "nowhere"].
When I meet someone to date, how can I communicate clearly that I am only interested in a casual/short-term dating relationship, such as dating for a few months by doing fun activities, going to parties, attending concerts, etc?