What exactly do you use it for. Is it saying I did that in the past and later I'm doing that or because. I'm confused.
Hi Anna,
ur guess is almost right, ~다가 is normally used when something happened while u were doing something
for example,
I think I sprained my ankle playing soccer.
축구하다가 발목을 삐었나 봐.
She opened the sluices while talking on the phone.
전화통화를 하다가 그녀는 와락 감정을 터뜨렸다.
hope it helped