Spotting

I’m 7 weeks today. At 6w5d I had the first ultrasound, in which everything was perfect. Perfectly steady, healthy heartbeat at 117. Last night around 1am, 6w6d, DH and I had sex. It wasn’t rough, nothing out of the ordinary. Just me on top, kind of slow, lasted around 10 minutes, then we fell asleep. This morning I woke up to pee at 7:30am. When I wiped there was dark blood on the tissue. I stood up and looked in the toilet, and there was more dark blood in the bottom. It wasn’t like liquid, it was more dry, flaky looking blood. But there was quite a significant amount. I called my doctor, she wants me to call in the morning to be seen again this week, and if it doesn’t stop or gets worse to come in. I’m having no cramps, just the occasional tug/pull that I normally feel here and there. But I am still bleeding, still dark. What could this be?