It sounds like a lubrication issue between the release bearing sleeve and the input shaft "snout". The sleeve that the release bearing is attached to is a metal to metal slip fit. I'm other words there is a smooth shaft that the release bearing assembly slides on. There is only a small amount of space between the two, just enough to allow for some grease for a smooth sliding action as you push the clutch pedal. When you release it, the clutch springs push the slide back to its relaxed position. So you are having to overcome the spring tension of the clutch pressure plate, which it the typical feel at your foot when you push the pedal down. When the slide grease dries out, or enough debris gets on the grease it dries out, so now you are having to overcome the dry, or non lubricated slide. Worse yet, when grease gets contaminated, it can act more like glue or sludge making it harder to push the pedal.
It also makes it harder for the clutch pressure plate springs to push the release bearing back to its relaxed position. Once the clutch pedal is released, the slide should return to the point where it no longer contacts the clutch pressure plate(or lightly touches). If the slide is gummed up enough the bearing cannot move away from the clutch pressure plate, and the bearing will continue to spin the entire time you are driving , which will lead to premature release bearing failure.
Unfortunately, the slide is housed inside of the transmission bell housing. The only way to access it is to remove the transmission/transaxle to remove the slide, clean it and reinstall it with proper lubrication. If you do this, I would replace the clutch parts while there. The major cost of a clutch replacement is the labor, not the parts. That being said you are looking at a clutch replacement.