My DD just turned four months too. Until she turned nine weeks old she was a pretty text book baby sleeping three to four hour stretches overnight. But then we returned from the UK and it completely wacked her out. At first it was jet lag but i believe my constant feeding her back to sleep in the night even when she wasn't hungry rather than patting etc caused this situation we have now. Which is she wakes hourly every sleep cycle and wants boobs or she cries! She also doesn't like baby wearing just me holding her. Its so tough.
I have found patting the mattress and rubbing her tummy works getting her to sleep usually now. And sure it would if i stuck to it overnight but don't want to wake the rest of family up, and i am often so tired i just want to get back to sleep asap. Waiting for my referral to sleep school to come through so i have space there to do this without worrying about anything else, so i can dedicate my time to it. But won't let her cry, will do it more gently.
Big hugs, i know how difficult it is! I kick myself everyday for taking her overseas so young and creating this problem!