could I be pregnant?

So I'm 9 months postpartum. I'm currently on the DEPO shot. And when I have sex my husband never lets it go in. So I don't see how I can be..however. Lately I've been feeling sick randomly throughout the day. I've been more tired then usual (and I'm always tired). Can't find anything to eat that sounds good. I took a test 2 weeks ago and it came back negative. All the tests I took with my first baby came back negative. So Idk if I can believe it. Could I be pregnant? Or just in my head?