Question about a low lying placenta at 24 weeks?

So I have had a low lying placenta since 15 weeks or before. I had a sonogram yesterday and it was still about 2 cm away from my cervix, they said its not a placenta previa but low. I have not had any spotting since about 4 weeks ago and it was very light then. I am on precautions of what I should not do. Well today I was talking to a "so called" friend and she was saying well "what if it rupters and this and that".....Do I need to be worried about things like this? I mean I know anything can happen and I pray that it don't but now I am worried about this. My doctor didn't seemed concerned yesterday and said that she highly thinks it will move up as i get further along. what do you guys think..i'm nervous now.