It's not that easy to understand your question. I wonder if you're using the words minor and major slightly out of context? There's more to major and minor than happy or sad. For example, this major chord progression: C, F, G will sound upbeat on its own. But it's entirely possible to create a sad melody over it. But it won't be a minor melody. And if it is, it will probably sound very wrong with those chords.
Likewise I do believe it's possible to create a happy song with some minor chords although it's more difficult than the other way around.
As for lyrics and rhythm, they're another thing altogether.
If you're stuck in a rut writing sad songs, maybe you haven't got to the bottom of all the sad things you want to say yet? Maybe you're just used to writing those things and have formed a habit. This can be hard to break - I know because I've been there myself, and had to force myself to use major chords where I normally wouldn't. Even with those major chords, my songs tend heavily toward the melancholy.
Without hearing your music or reading your words, it's not possible to give much better advice than this. But if you want to starkly hear the difference between one of your songs and a major, happy song, compare your song with Pharrell's Happy. Take it apart, see how it works, and try to apply the knowledge to your own writing. You never know where it might take you.
One last observation: there's nothing wrong with sadness. It's what you do with it that counts. If your songs are all tip quality, people will like them whether they're happy or sad. So you've got to allow a certain degree of being yourself if your songs are going to carry any authenticity. Don't forget to have fun with it.