My girlfriend always is underneath me?

I love my babygirl to death but she always wants to cuddle with me when we go to sleep i dont mine when were just chillin...but when we go to sleep i need my space some times,i mean i dont care sometimes il even cuddle and kiss her when were about to go to sleep but its like everytime...she falls asleep huggin me on my chest and i push her off but then when im have asleep shes on me again i tell her she needs too give me my space when we sleep and she got sad and she has these big wide blue eyes and when she started poutin i felt so bad.?HELP ME!