Most Helpful Guy
I've personally felt that way in a past relationship. I spoke to my partner about it and she told me that everyone has something they are looking for.
For guys it might be a beautiful woman with a slender body, others could be the larger lady.
People can't really know what the other is thinking but we all have something we look for in a partner. Instead of thinking "why are they with me, they could do better". Think of it like "Wow this person could do better but chooses to be with me".
It's all about finding the positives in the negatives.
Most Helpful Girl
Yeah they do. If their girl is really great they start to question why the girl is with them. Lots of men even come right out and admit it. The man may be feeling inadequate. I think when that happens its best for the girl to calm their insecurity with reassurance; that they are together and she chose him and loves him.