Crying to sleep

My LG, for the last few weeks, had been crying while I put her to sleep whether its for day time naps of her actual bedtime. It doesn’t matter if she’s just started to get tired, or shes already moaning but as soon as me or my husband starts to try putting her to sleep, she starts crying loudly. I have to rock her really vigorously for her to eventually sleep or just stick my boob on her and then she’ll fall asleep. My arms and backs aching and nothing else seems to be working. I’m EBF but this week I’ve started her on solids (so far steamed carrots) and she’ll be turning 6 months next week. She has around 3 naps a day which mostly last 30 mins (sometimes up to an hour)