Unusual period

Okay so, my freshmen year of highschool I got put on the depo shot. Well April of last year I got taken off it, it took about 3-5 months for me to get my period and a regular flow back. Ever since my periods have been normal, glow is so accurate about them. The first day they are usually pretty light, I wake up with blood in my pants and all. the second day they are usually terrible. But I usually don't ever get cramps. But this time I started getting cramps two days before my period started. The day that glow said I should start my period, I got up out of bed, there was no blood in my pants. So I went to the bathroom and there was a little bleeding. And it's now the second day and my period has completely gone away. Me and my boyfriend have sex constantly, without protection. Not trying to get pregnant but not like worried about it. Like if it happens it happens. Ya know? Anyways I'm just curious as to why? Like does anyone else have this problem? Could I possibly be pregnant? Hmmmm