Hcg levels

Hi mommies!

So I have a few questions. On Friday 3/20 I turned 6 weeks and my hcg results were 1772. On 3/23 they were 2760 and on 3/25 the were 3371. On 3/30 I'll get yesterday's results at my appt.

On 3/20 they did an ultrasound, yhry seen a sac but had a hard time seeing anything in it, so they're doing another ultrasound on 3/30.

since 3/25 I've been having brown spotting with occasional cramping, I mentioned to the dr she said come into er if I start soaking pads or hemorrhaging. I'm just confused as to why I'm having this brown spotting, occasionally it's pinkish.

Could I be miscarrying even though my levels are rising? And why aren't they doubling? Help!