I only tried Gas-x briefly, but if you find your gas symptoms are worse at night try taking one after dinner, and one before bed. I'm not sure what the dosage for them was, if it says take 2 at a time then you can try that.
As for the fennel seeds, it should work as well as the tea, except that the warm liquid of the tea is also soothing for cramping and pain. If you're more focused on gas then you probably don't need the warm tea. Try taking a big spoonful of seeds and chew as much as you can.