use 1/8 teaspoon of psyllium seed husk (same thing is called colon cleanser, like metamucil without any sugar). HEALTHPLUS makes a great brand and is very inexpensive and sold at most health food stores.
then make sure to keep fresh, clean water available at all times. it is important during this time to change the water bowl 3 times per day. it may look clear to us, but try holding it up by the window in the light and you will see dust and hairs in it. it is ULTRA important to make sure the cat drinks lots of water when constipated.
also, STOP THE PETROLIUM JELLY THING.
instead use petromalt hair ball gel. it's for hairballs but lubricates without being too harsh.
what i did was put the powder (psyillium seed/colon cleanser) in little bits of the petromalt and rolled in small balls in the palms of my hands and then administered like a pill. but you may be lucky and your cat may just love the taste of petromalt and if so you can just let him/her lick it off, but put the psyillim seed powder inside the petromalt to get it down.
nice massage and gentle petting will also help your cat.
if your cat like grass that is good too.
and buy some fresh cat nip buds COSMIC CAT at petsmart and let your cat roll in it and sniff it and snuff it up it's nose. this is a great herb to help but must use in conjunction with the psyillium seed.
sounds like your cat is not drinking enough water and that can only mean your cat wants it changed 3 times a day, maybe it's in a traffic area where too much dust and hairs are in it, or in an inconvient place. - or - your cat is simply eating too much.
keep us posted. stay off the laxatives, use psyillium seed (it's like powder) and the petromalt instead)