Hi beline! It looks like you are in France - I'm in the US - nice to meet you. I don't know about French grammar but English grammar is almost 180 degrees opposite of Korean grammar, so in many cases of translation we can almost start from the end of the sentence and work backwards.
In your example "널 사랑한단 그 말이 자꾸만 부담이 되나봐 그런가 봐" it may have been spoken as a single sentence in conversation but I see two sentences loosely joined for emphasis "널 사랑한단 그 말이 자꾸만 부담이 되나봐 (It seems that saying the words 'I love you' has often become a burden to you)" and "그런가 봐 (It seems like that/this)"
Looking at it as a single thought: "It seems like I have often laid a burden on you by saying the words 'I love you.'"
The methodology:
(Note: over time, once the mind becomes familiar with Korean grammar and nuance, there is direct understanding of what I call 'units of thought' and word-by-word translation becomes moot.)
First we get a literal, as it stands, translation by looking up
http://dic.naver.com/ the possible meaning of root words:
널 사랑한단 그 말이 자꾸만 부담이 되나봐 그런가 봐
너를 -you(object), 사랑한다는 -love doing, 그 -that, 말이 -words are, 자꾸만 -frequently(with emphasis), 부담이 -an imposition, 되나봐 -becoming seems, 그런가 -that+?maybe/might + 봐 (보다) -to see, observe = appears
coarsely put together:
'you loving do those words frequently a burden becomes it seems, it seems that'
Finally: "It seems like I have often laid a burden on you by saying the words 'I love you.'"
hmmm? Not nearly as poetic as the Korean is it?
Perhaps Julia or one of the other teachers could give us a more romantic translation?