My 5 month old has been a reasonable enough sleeper so far. For the first couple months, need a lot of movement to nod off but by 4 months, this had settled. We’d mostly weaned her off the movement thing, maybe a small rock of her rocking crib here & there but she’d settle with a dummy & muslin to fiddle with (which I remove when asleep).
She’s just turned 5 months & for the last 10 days, we are back to square one. She cries & cries & cries until she drops. Doesn’t matter if you cuddle her or put her down, keeps crying. She’s really tired, rubbing her eyes, yawning.. all the usual sleep cues. She still has her muslin & dummy (although she cries so much, it’s never in her mouth much). I pick her up, sing quietly, rock .. keeps screaming. I pop her back down & rock her crib. Screams. Basically for 10-15 mins until she finally falls asleep. 
I hate it. I hate her crying. And I hate that it’s clearly just from being tired & unable to settle herself like she used too.
Any ideas? Is this just a developmental phase? She’s fine once asleep. Naps OK & sleeps 12 hours at night with a feed around 3am-ish. It’s just the getting to sleep that’s horrible 