Jiban bro I dont know what to say. Like everybody says who has the problem he feels it more. So I cannot imagine the real problem here. I think the best thing is to sit down and talk about it. If you think you are having a mental problem due to this relation then you have to sit down and talk. A girl does not mean so much, unless she is your wife. Even with wife you need to work out by talking. Any way she is supposed to be your best friend. Share everything and dont kill yourself  inside by thinkig too much. if you think you cannot handle this then end the relation. Like devroad said live free. Dont think too much. Live your life. You can even give a try by using some of these devices that our friends has suggested here in sajha, If u think it will give some answers to your quetions.