First of all there is no need to be alarmed by this and certainly no need to worry. If she wants you to wear her panties during a sexy session then this is a harmless fetish or fantasy. Fantasies and fetishes can play a huge part in people's sexual relationships. Sex doesn't always have to be serious stuff; it should be fun for both parties. However, if you are not comfortable with this, or just don't want to participate then don't do it. Explain to your girlfriend that you are not happy wearing her panties, if she loves you I am sure she will understand, the same way as I am sure you would understand it if the situation was reversed.
There are many reasons why people have these fantasies or fetishes, only she can answer the question why, it could be that she is just curious to see her manly boyfriend in something feminine. Maybe ask her why.
But if she wants you to wear her panties on a daily basis instead of wearing your own underwear then this could be that she just wants to feel that she's near you 24/7. Maybe she is a little insecure. Some girls like the idea of wearing their boyfriend's shirt for bed just to feel close to them. But again if you don't feel comfortable with this then you need to tell her that you don't feel comfortable. There are many men that like to wear women's underwear purely for the softness and the feel of the material which is generally softer and more comfortable to wear. Many girls are not happy with this at all and think their boyfriends/husbands are a bit strange. But as long as you are both comfortable with the situation then there is really nothing wrong with it at all.
There are many reasons why people have these fantasies or fetishes, only she can answer the question why, it could be that she is just curious to see her manly boyfriend in something feminine. Maybe ask her why.
But if she wants you to wear her panties on a daily basis instead of wearing your own underwear then this could be that she just wants to feel that she's near you 24/7. Maybe she is a little insecure. Some girls like the idea of wearing their boyfriend's shirt for bed just to feel close to them. But again if you don't feel comfortable with this then you need to tell her that you don't feel comfortable. There are many men that like to wear women's underwear purely for the softness and the feel of the material which is generally softer and more comfortable to wear. Many girls are not happy with this at all and think their boyfriends/husbands are a bit strange. But as long as you are both comfortable with the situation then there is really nothing wrong with it at all.