What's your weight like? I've had amennhorrea (sp?) on and off over the years and it's always been related to being underweight. All three of my children were conceived when I made a conscious effort to tone down the exercise and increase my calorie intake.
I NEVER have periods-ever!!! I have pcos needed clomid to conceive, before I was given that I had provera to give me exact period days to take the clomid on, but still didn't have a period. Had a baby which has kick started periods again, now naturally 13wks. You might just need a bit of help getting there but if all your test are coming back good, do they show that you are ovulating?