Hi, you sound like such a lovely caring girlfriend, Im not sure if this will help, but as a english artist who's up for a big of sm, all I can say is go slow and experiment first, maybe light bites on her body and (spanking) see how she reacts, then maybe then harder, as soon as you see thats shes enjoying herself you will be fine. She probably wants to make you feel happy as much as you want her too. and have fun