Hi, sounds tough on you right now.
Just a couple of questions....is reflux medicated? Can you post your EAS so we can get an idea of what your day looks like? Do you rock to sleep?
18 weeks is still young and waking through the night to be expected in some, my DS2 also has reflux and is 25 weeks and has only slept through once properly. Constant waking often indicates discomfort or the need to learn to self soothe.