Glad you're feeling a bit better about things. I think sometimes it's necessary to adjust our expectations a bit. We're told all sorts of things about what babies 'should' be doing and there's all kinds of 'receieved wisdom' about what's normal, but little of it actually corresponds to real-life experience.
19 weeks and feeding 4 hourly, waking only to feed and sleeping well otherwise = very very good sleeper!
Just give him time - I honestly doubt you need to do anything, he'll get there soon enough.