clutch problems?

i have a h reg fiesta 1.1 latley ive noticed that every now and then when i press the clucth pedal it makes a knocking noise and feels like i loose a bit of resistance from it also when this happens i have to release the pedal then reaply it to get it into the gear like i said it sounds like its coming from the pedal does any one know whats wrong and how do i fix it