When you are lost, you need a compass. Think about it.
Seriously, if u trying to be sacarstic...i curse wen such things happen to u...u'l suffer.
You probably feel more sympathy for her than love. Perhaps u feel obliged to take care of her, since to you, she's ever so vulnerable.
Personally, i feel that if u have thoughts of "am i settling for second best" in your mind at this stage of your relationship, this question will probably stick in your mind, as long as you're still together with her.
As time goes by, you start to believe that you are settling for second best. You'd probably start to find that she's getting on your nerves & starts to pick on her for every little thing that she does & the relationship gets affected.
True love is not sympathy. When you truly love a person, you would never think he/she is the second best. You would be thankful that you found him/her, and not somebody else.
Maybe you already have a decision. You just need the courage to make that into action.
Cheers!