EBF but concerned about pregnancy.

So I know this sounds absolutely bonkers. I have a 7 week old. I am EBF and he still wakes in the night to eat, although only for about 5 minutes. Last week I started getting some cramping and nausea. With that came headache and straight up exhaustion. I am also unsatisfiably hungry. I just want to eat constantly. The weird thing is none of these symptoms started (well to this extent) until last week. My cycle hasn't returned so I have no idea a time to test. But it's most likely just new mommy stuff right?! I don't think I could be pregnant. I've had unprotected sex, but doc said that they was safe to do for about three months. Thoughts?!