I feel the exact same way on weekends! I always try and plan out things to do with friends so I don't feel this way, but it's inevitable that sometimes I won't have anything to do and will feel lost and just lie around thinking about myself, which I am doing now.
I feel SO incredibly lazy right now, and I hate it! I need some structure in my life to keep me busy and keep me from thinking about myself too much. So I do know how you are feeling; you're not the only one!