Should i wear underwear to bed at night usually i don't but it is winter should i?

There is no right or wrong answer to this question. It is basically healthier to sleep totally naked as that allows your entire body to fully relax and the skin to breathe and rejuvenate.

Wearing underwear in bed will add so little that it will not really keep your body warm. It is better to add an extra sheet or blanket than to directly encumber your body with unnecessary clothing.

It's very healthy to leave underwear off in bed. If you are cold though, keep them on. Otherwise it's good for you.

Up to you-- if you have a normal heated home then why wear underwear? Add a blanket if the bed is cooler. Then you can let your boys breathe.

Leave your underwear off, it's more comfortable to sleep naked. I sleep naked all year round.

Do whatever makes you comfortable.