Human Dummy!!

Hi everyone. My little girl is 17 weeks old and I'm really enjoying breast-feeding her. However, recently I'm starting to feel as if I'm being sucked to death! She used to go a good 3 or 4 hours between feeds and this was fine, but now she seems to need to sleep more during the day and the only way I can get her to sleep for any length of time is if she is left on the breast. That means I have to sit on the sofa with her latched on for up to an hour at at time (in the afternoon we both go to bed for 2 hours and she stays latched on most of this time too). I wouldn't mind doing this as I feel this period lasts for such a short time and who wouldn't want to be cuddled up to their favourite person if they had a chance, but I can feel my nipples starting to get tender again and I def don't want to go down that route again!!!! Has anyone had a similar problem? What did you do? I don't think a dummy is the answer as Ella won't take anything plastic into her mouth!! Thanks ladies