the pineapple needs to be fresh, and will only (possibly) help if his trouble is that he's molting (shedding really badly) and has a hairball. I definitely would NOT give him olive oil.
he needs to see a vet ASAP, as bunnies can go downhill very quickly and it's considered a medical emergency if they don't eat and/or don't poop for 8-12+ hours.
until you can get him into the vet (which really needs to happen today), you need to do what you can to get him to eat and make him comfortable.
pain meds are very helpful - give metacam if you have it (you would've had to get it from the vet at some point), if you don't then you can use baby aspirin, low dose aspirin or baby ibuprofen. here's a site with dosing info:
http://www.medirabbit.com/Safe_medication/Analgesics/safe_analgesics.htm
if you have critical care food (comes from vets), you can syringe feed that. if you don't, you can make a pellet slurry - take some pellets and add water or pedialyte; microwave. let sit for 5-10 mins so the pellets can "fluff", then mix together (breaking up the pellets as much as possible); add more liquid if needed to get it to a good pudding-like consistency for syringe feeding. critical care will work with a syringe as-is but with the DIY slurry, you may find it necessary to cut the tip of the syringe off to make the opening larger.
you can also offer him a little bit of canned pumpkin (PLAIN stuff, not the pie filling kind) and/or some fruit or squash flavored baby food... not a whole lot, as these foods are sugary - maybe 2 tsp or so. if he won't eat the pumpkin on his own, you'll need to water it down with water or pedialyte in order to easily syringe feed it. these things could also be mixed into the pellet slurry or critical care to make it tastier.
you should syringe water or pedialite if you're worried he might not be drinking enough and/or if you're feeding pellet slurry/critical care.
when you syringe feed a rabbit food or liquids, you want to aim for the gap between his front incisors and back molars and always squirt the food/liquid in sideways - never straight back - to make sure he won't accidentally inhale it. remember to give him time to chew/swallow. I find it easier (especially with liquids) to have the bunny wrapped in a towel, as things can get pretty messy.
here's a great video showing how to syringe feed - [ame]http://www.youtube.com/watch?v=8iGZVYVm5Bg[/ame]
simethicone (any brand of over the counter baby gas medicine) can also be given. it may or may not help depending on the cause of the GI stasis, but it's *incredibly* safe for rabbits so it definitely can't hurt. you can give 1-2 cc every hour for 3h, then 1 cc every 3-8h as needed if it seems to be helping.
here's a good listing of rabbit-savvy vets if you don't already have a vet lined up (not all vets willing to treat rabbits are actually rabbit-savvy!) -
http://rabbitsonline.net/view_forum.php?id=9
