No period, four negative tests?

HELP?! Im loosing my mind here. I already have a little one (whos soon to be two in december). I stopped taking my pill march and ive always worked like clockwork not ever a day late nor have I ever been. I came off my period on the 2nd of may on the 12th of june i had the symptoms id had with my first so took a test on the off chance - negative. By the friday i was still so convinced - negative. I should of come on my period on the 26th but i havent and it should of been ending tommorow but still nothing ive taken another two tests this week but both negative. What would you think? Im starting to feel like im telling myself im pregnant but is there any other reason there could be for not having a period? X