Hello. I am a beginner playing about a month. I am developing right shoulder and trapezius pain. Feels like tension. I think I have good posture. Any tips out there?  I have a full size acoustic guitar. Should I hold it in a different way?  Shoul I get a 3/4 guitar. Having the right elbow up so high from the guitar feel off for me. Or should I just keep going for now?  Thanks.