New construction, I just wired 2 receptacles and the bathroom light and fan , plus another ceiling light on the hall to a gfci breaker . When I finished , I popped in a 15 amp breaker to test the circuits , everything worked as usual. Well , it dawned on me that I had had not installed the gfci breaker and I installed it last night . As soon as I flipped the breaker , I walked to the bathroom to test the bathroom light and instantly it popped the gfci breaker . I turned the light off and reset the breaker . I tried one of my plugs and as soon as I plugged it a work light , it popped a breaker . I turned it off and with my Kline tool test light that turns red when close to hot wire and stays green when near a neutral, I tested all the circuits. When I get near the neutral it stays green but when I check the ground , it quickly flashed red then green . Does this indicate I have a ground fault somewhere? I was reading on another post where a screw or staple was the culprit .

All for circuits run a junction box and connected together , all black , white and grounds are connected in groups .

Am I thinking on the right track ?