4 month old waking during night?

I had the very same problem with my daughter. When she started sleeping on her own, her dummy would fall out, wake her up and she would need it put back in and a rub. This continued for a week or so, until I was getting less sleep than when she was first born. I realized that during the day I was so tired and therefore not being the best mother I could be, so I weighed it up and let her cry it out. She cried for about 3 hours, (it was horrid) but after that she settled herself and went to sleep, and has done ever since. She is a very happy child and still loves me and her daddy, so I don't think it caused any long term upset. Always follow you instincts, you know your child better than anyone else. Hope this helps. Good luck!