Thank you for paying it forward with some great advice V!
Welcome to the forums LaraAndrea, lovely to have you here.
It might be useful to note that Tracy did say in her book that some LOs don't make it to the 4hr E until 6 months. She lists a couple of examples including low birth weight, prem, BF...but my DS was none of these and still he couldn't make it beyond 3hr E until he was 6 months old and on solids between the milk feeds, so there are LOs who do need to stay on 3hr E. If your LO is one of them that's fine - I hope that the advice given by pp also helps.
4 months is a typical time for sleep regression, my own went from 2hr naps to 40 mins naps five times per day too - wow it's exhausting isn't it. The good news is that often these LOs get through this regression around 6 months so whilst it might feel like for ever, it really isn't.
Would you like to post your EAS times for us to look at?