The last week or so every feed is a battle...she'll take the first 20 or 30 mls fine but then starts squirming around, arching her back, sticking her thumb in her mouth and crying. Once she settles down it is a real struggle to get her to drink anymore as she'll always try to have her thumb in her mouth, or she starts crying. I don't know what to do...she used to be fine and was happily drinking 180ml a feed, now she is lucky to have 100ml, I can sometimes squeeze 120ml into her. She's 'supposed' to be having around 240ml per bottle now as she is over 4 months, but I would just be happy if she'd start having all her 180ml bottles.

What could be wrong? Have tried burping her but nothing comes out. I am still using the size 2 avent teats, I did buy a couple of size 4 (for 6 months+) today so will sterilise them now and see if that makes a difference, could she just be fussing around because it isn't coming out fast enough? But it's not like she is hungry, she just seems to not want it. She isn't sick or anything and is perfectly normal at all other times, just turns into a screaming monster when I go to put the teat in her mouth! Nothing has changed in the last week or so...

Please help!