hi mate, first things first, jack it up and have a look on the underneath. if its pulling to one side u may have bent the driveshaft, or twisted the wishbone. as for your seat i doubt it was to do with the bump because if it was you must have a huge dent in the floor, and you would know about it if you did, just have a look on both sides and check for anything that looks bent or twisted. if nothing is bent or twisted, keep your car jacked up (at the front) and move the steering wheel side to side, you could use a second pair of hands to look while your moving the steering, you might be able to see then what it is thats making it like a boat. hope this helps, let me know bud.