pregnancy or birth control? weird symptoms?

Hey! I have been having some weird symptoms recently. I had been on birth control for years and recently had come off of it. I have been having very dull cramping for the past few days. Sometimes I wouldn't feel anything at all for hours and then I would cramp again. When I was on the pill I'd start my period at about 23 days (with 5 days of the sugar pill) so I had been thinking maybe I was due to start with the weird cramping and all. Well, that time has come and gone and no period and no bleeding. I took a pregnancy test and it came back negative. I'm wondering if maybe I'm just testing too early and maybe my cycle now isn't going with the cycle I was on with the pills? Any ideas? Or could all of this just be my body adjusting to not being on the pill after years of being on it?