Ttc #3

My husband and I are ttc baby number 3 and praying for a girl as we already have 2 boys. My period was suppose to start on the 25th of this month and it hasnt. I've taken 3 test and they all said negative but my lower back is constantly hurting and I've been really crampy. Today was the first day in maybe 3 or 4 days I haven't felt like this and my mom thinks I'm having my period without bleeding...is this possible? And how will I know when I'm ovulating??