Larry is right. Frost heave in the ground has probably knocked everything out of level. Not a fun job to crawl around underneath with a jack to fix. Have a lumber yard cut some 4" or 6" wide shims out of oak to shim the trailer above the blocks. The trailer rails/beams will just smash those cheap cedar shims used for shingles and shimming doors. Build a block and wood pier in the middle of the trailer and check and establish the high point with a laser level. Have someone stay by the level and turn it (keeping it level) while one or two others find the logical starting point and move down the trailer jacking and releveling as they go. Do one side and end at a time. Then move to the other. Fix all blocks and pad as they go. Dig under the concrete block pads to make them level if they aren't.
Since it is probably to old to stand up to a move and you won't anyway, consider a more solid foundation. A poured footing down to frost depth and a stem wall all the way up or a block wall.
As a minimum, support it like you would a deck. Unless you have a shallow frost depth, it may be too hard to dig some 8" round holes for piers underneath the trailer frame which sets in about a third of the way from the side. If you have 3' frost depth like we do, I would remove the skirting and get a power post hole digger and go around the trailer digging holes for piers and try to start inside the skirting line and drill on an angle. Use rebar and some of the cardboard tube to form up to where they are all level and then fill them with concrete. Jack up one end of the trailer and start laying support beams across a set of piers to support the trailer. Preplan the number of beams and thickness, number of holes, and height of the holes. At 14', I'd probably go ahead and put blocks under the main trailer rails for additional support. Use the pier holes to install your tie down anchors before adding the concrete(to really make them solid). If you don't have them, then put some in. Do this for your addition too. Then reapply skirting. Good luck.