Spotting brown uterus stretching?

I have been spotting brown only when I pee and wipe, and have been feeling sharp tings on my sides and stretching. I’m 10 weeks 2 days today. Could that potentially be the reason for the brown spotting does that seem normal?..

I’ve already had 3 ultrasounds at 5,6 and 9 weeks they all looked good, and ahead of schedule but it’s still worrisome

I do have a second twinB sac with nothing in it so my doctor doesn’t know if it’s from that or just me stretching expanding….