-다 싶다 means "it feels like, as if maybe; think to oneself that" it is used after a plain style quote. e.g. 피곤하다 싶으면 영락없이 도진다. Whenever I feel tired, it hurts like hell. 지난 번이 마지막이다 싶었는데 또 친구에게 아쉬운 소리를 해야 한다. Although I felt that was the last time, I must ask a favor to my friend again. 한국 사람들은 사적인 일에 관심이 많다 싶어요. I get the feeling that Koreans have much interested in private stuffs. 먹어 보면 돼지고기다 싶지만 사실은 콩으로 만들었어요. When you eat this, it will taste like pork, but it is actually made from beans.

* ~고 싶지만 : want to do something but ... * 먹어보면 돼지고기가 싶지만 => 먹어보면 돼지고지인 것 같지만 * ~인 것 같지만 : As though it were ~