I'm 145 lbs and I break spokes too. Don't let it discourage you, it's part of riding.

NDS spokes break at the J bend when the tension on them is not high enough. They momentarily go slack as the part of the wheel they are in passes the ground (the rim flattens slightly). The cycles from no tension to tension fatigues the spoke at the bend, and it eventually breaks.

There's a number of things to address this. First is to make sure the DS tension is high enough. The DS tension along with the hub geometry determines the NDS tension needed to center the rim. More tension on the DS means you can tension the NDS higher. The allowable DS tension depends on the rim- too high and the rim will eventually crack. A good builder should tension the spokes high enough but sometimes they don't.

Next you need a hub with good flange spacing. DA and Ultegra hubs are pretty good so I expect 105 is too.

Then you need appropriate spokes. I would guess you are using 2.0/1.8mm diameter spokes. Some spoke makers like Sapim will use 2.2mm at the J bend, making the spokes a bit stronger there. Of course you need quality spokes. Sapim, Wheelsmith, DT are all good. I've had fewer Sapims break than other brands but that may be due to me building the wheels vs a shop. (not that I'm better than someone who has built hundreds of wheels, but I can take my time, and I can build wheels specifically to address my spoke breaking problems).

Another trick is to use smaller gauge spokes on the NDS. They will need to stretch farther to reach the same tension, so they are less likely to completely detension and start fatiguing. I've built some wheels like that (using Sapim Race, which are 2.2/1.5/2.0) and it seems to work.