Playful - difficult to let her suckle directly

I feel like giving up breastfeeding. I have very bad sore neck, shoulder, stiff and unmoved. She can't suckle long enough to get herself full, just less than 5 mins, she lets go the nipple. :( how frustrating.........

Now when I have so much milk, she refused to suckle ....and very playful and can't concentrate. I have to cuddle her in a quiet place and sometimes sing "mama" song to her. btw bethanie likes the song, everynight before she is asleep, she always asks me to sing this song for her.