Yes, as Matty mentioned it is talking about one's experience. The standard form would be "고생이더라" - it was a hard going / it was tough. 고생: hardship; tough going; ordeal (이)더라: I had the experience of ; I saw it that... "개" before 고생 is a prefix emphasizing the degree of 고생. It is not good style (fells like street language) and is mostly used on the internet. Better be careful with using such words as they are come close to swearing.

I'm not a native speaker, but it literally means --> "I have experienced hardship", but in general it may mean "I know what you mean" when you sympathize with someone over something, that you may have experienced [ "더라" = "더라고요" = "데요" (I think) --> is a grammar point used when you want to say 'you have experienced something first hand', it is past tense always. If you said "저는 한국에 갔을 때 비가 오더라고요" --> When i went to Korea it was raining VS. "저는 한국어 갔을 때 비가 왔더라고요" --> When I went to Korea it had already rained. E.g: 나) 나는 매일 매일 아프느라고 이번주에 아주 어려웠어 마) 아, 개고생이더라... I may be wrong, but this is how i understand it. Hopefully this helps!