How to wean almost 18 month old?!?!

My daughter will be 18 months on the 22nd and she only nurses at nap and bedtime to fall asleep. But once she's asleep at night she normally stays asleep. But naps she has to be nursing or it has to be touching her cheek. I don't mind but I'm 23 weeks pregnant and she will twist and turn while still latched an I'm sore already but how do I get naps to be like bed time? Thanks in advance.