I would take it to the bike shop. If it is that outer-ring that moves, then it could be the threads. Bad business, that. If it is the inner-ring, then at a minimum you need new bearings, but probably an entirely new bottom bracket.
Either way, the warranty from the bike shop should cover this. You are not too heavy for that bottom bracket. I'm much heavier than you, and only had to replace a similar BB after about 6500+ miles or so. Lots of big guys only get 3500 or so, but it should last you A LOT longer than this.