hi Chilli. What time of year did you conceive in the past? It's just that we're mid-winter now and so there's very little light. I've read that using a light box might improve fertility. Because our hormones are in hibernation mode? I guess we don't know what to believe when we read so much.
I am just sleeping so much and get seasonal affective disorder so have ordered a new light bulb for my light box. If nothing else it definitely gives you loads more energy and lifts your mood. But some folk believe it's the sunlight that causes so many people to get preggers on their holidays.
Is there anything else you are doing differently, diet, lifestyle? I'm having the same problem exactly, quick to conceive in the past, not working now, even with perfect timing and EPO mucus. I go crazy every month convincing myself of every symptom, I even get implantation pain, then the witch comes (today). Fingers crossed for you.