Naive first time mummy thinking she had a great sleeper... All hell broke loose at 13 weeks!

[PhiePhyPhoPhum]

Sorry for my dramatic thread title, I've had under 3 hours sleep & feeling a bit loopy!
My DD is now nearly 15 weeks, until she was 13 weeks she slept fantastically, from around 7/8 weeks she was sleeping 9-9 with a short 10 minute feed between 5&6 some nights she dropped this feed completely but slept through till 8, there I was feeling smug that I was getting such a fantastic nights sleep but oh my it has all gone to pot!
We're on several wake ups a night now & she will not settle at all after them, takes a good hour or even two sometimes. Some nights over the last two weeks she's take 4+ hours to settle, I feed her to sleep usually bad mummy but if she wakes up when I put her down she'll often self settle, the last two weeks it has been screams after about 5 mins of being put down about half the nights, the other nights she goes down without a problem but is awake an hour later.
She'll then be up anywhere between 3 & 8 times a night before finally deciding it's playtime between 6/7. I wouldn't mind the wake ups at all if she could settle quickly like she used too afterwards but now I have to sit over her holding a dummy in her mouth as she won't suck it on her own or keep cuddling her till she falls back to sleep, some nights it can take hours & by the time I've settled her I'm so over sleep myself thus only have around 3 hours a night.
She doesn't nap in the day at all, I've just come to accept that now. I think she's got reflux which I'm calling HV about today but she doesn't seem as bad at night. I also think she's teething already & can feel them under her gums, I'm using Bonjela & Calpol for this.
A thought occurred to me last night however that could she be too cold? To sleep she wears a vest, sleepsuit & 2.5 tog gro bag & room temp is between 16 & 18 degrees which is right by all the books & info I read. Would I be wrong for getting a 3.5 tog gro bag? I don't want her to over heat but when I put her in bed with me last night she slept better (my thought is because of body heat), I didn't as I was that panicked about rolling over & hurting her.
I don't know if that makes sense, I'm that tired I can't even be bothered to read it back through but wondering if anyone has any advice or similar experiences?

My DS was like this at the same age wouldn't nap in the day and very very disrupted sleep at night. Things that helped were:
He WAS cold, and since then whenever he been cold his sleep has been worse. His bedroom is usually between 20-21 degrees and he has a long sleeved vest, all in one sleep suit and 2.5 tog grobag. Any colder than that and he struggled to sleep. He's better now he's older and can wriggle about to get himself comfy/cosy.
Try and get naps sorted. Look at Gina Ford for timings and get daytime sleep whatever it takes at those times. I took DS on two massive long walks/drives a day for weeks to get those naps in, and then worked on transferring him to the cot at those times. Mini routine of grobag, darkened room, kiss goodnight and bung in cot. (Run away, put kettle on!)
Try white noise-we have an old radio playing quiet static, quite soothing

Good luck!

He could be cold - both of my dd's, at that age, had their rooms at around 18-19 degrees and they wore a vest, sleep suit, 2.5 tog sleeping bag and a couple of blankets, they just liked being toasty!

My DD did the same. Started sleeping through at 6 weeks. I tried not to be smug but it was great! Then she hit 13 weeks and it went to pot. I think was a growth spurt and teething.

Temperature wise I find the room often feels cold even if the temp read 16-18 degrees. We put an oil filled radiator in her room and just have it on low and it really seems to help.