CharChar, the temptation is to come onto a thread like this and say 'its perfectly normal, don't worry
'
But I know that by this age, with DD1 I was a the very end of my tether. I didn't want to hear 'It's OK' I wanted to hear 'I hear you, and I understand your concerns, and you are reasonable to be concerned.'
I have had 3 children who needed extensive support to get through the night.
DD1 - has never cracked it, tbh. She has melatonin to sleep, and she has significant SN, which were only diagnosed at 2 years 9 months. She screamed all night long for her early life, then slept fitfully through the night thereafter, waking several times each night. Even now, with the melatonin, she wakes each morning between 05.00-05.30, depending on how much she has woken in the night.
DD2 sounds like she was similar to your DD. She had reflux, treated. One night, at around 4-5 months old, she arched her back, screamed and looked simply terrified. She WOULD NOT lie in her crib. She was terrified. We moved to co-sleeping. Then, at 13 months, I'd had enough. I night weaned, using the 'no cry sleep solution'.
Basically, I set a time in my head that was the end of 'daytime'. I chose that time to be 11pm. So, she was put to bed at 7pm, and breastfed. Any time she woke between 7-11, she was fed. At 11 pm shop shut.
Now, that meant that if she woke at even 10.58pm, she was fed. But if she woke at 11.01 pm, tough luck. I used to wrap my duvet around my chest, so that she didn't smell my milk as much, and comfort her, but DID NOT feed her.
She wasn't chuffed at first, but soon got used to the system. I won't lie, it took almost a year to get her to sleeping decently. But now, barring nightmares, etc, or toilet needs, she sleeps through the night.
DD3 was similar to DD2, except that she didn't have reflux/cot fear.
If you DO have concerns about your DD, then you need to PUSH. Ask to see a developmental paediatrician. They can do some simple games with your DD, take a history, and either say 'nothing to see here, enjoy her' or 'ok, well your DD's going to need a little extra help, let's get that organised.'
Don't despair, though, it won't be forever. We now have 2 girls that sleep pretty much through, and 1 that has help to sleep for a good chunk of the night.