DD is 3&1/2 months and has never been a good sleeper, slept on me at night from 4 weeks to 11 weeks as she'd just scream in her crib. Finally got her into the crib after some persuasion (plus hot water bottle to warm crib, rolled towel round edge to make it cosy, swaddling and prince lionheart bear womb noise) and after about a week she settled back into the sleep pattern she'd had on me - going to sleep between about 830 and waking between 12 and 2 and again between 3.30 and 5, sometimes in between too, often not really going back to sleep properly after this second feed. She's EBF and a bottle refuser.
In the last week she has started waking much more frequently, every 1/2-1&1/2 hours. Occasionally she can self settle, sometimes the womb sound works but often we resort to white noise (hairdryer) and if all else fails another feed and starting the whole cycle again. Sometimes she wakes just 1/2 hour after she has gone down at the start of the night and keeps waking that frequently nearly the whole night till her day starts at 4.30.
I'm at my wits end and crying with exhaustion 
. She is a poor daytime napper too, will only sleep on someone (mainly me after a feed but occasionally DH) or in the sling, occasionally in the car if exhausted but often just cries there.
I've read about the four month sleep regression and wondered if this is it come early? Has anyone else experienced this problem and overcome it? Any advice or words of reassurance would be much appreciated 
.