Period with no blood?

I think I'm due to start my period today, but I haven't bled one drop. It's so weird though, because I feel like I'm on my period. Crampy, and the feeling that your tampon is too full, or like something is coming out but nothing is. Negative HPTs and <2 HCG blood test. I've also just barely stopped getting positive LH tests. I've been having them for a couple weeks. I'm on CD 35. Anyone have a period with no blood? Is that possible? Am I crazy?