Anyone experience the hook effect with hpt's?

I'm 6 weeks and 2 days along and a nervous wreck since I had a miscarriage in April and a chemical in July. I've been taking pregnancy tests for reassurance to see the lines get darker. Last week the line was super dark and the control line was light. Then I took another one yesterday and the control line and the test line are about the same color again. Does that mean my hcg is decreasing?!? I freaked out and went to the doctor who let me get an ultrasound which revealed a baby measuring 3 days ahead and heartbeat of 113 which they said is normal for 6 weeks. But I'm still worried about the control line and test line on the hpt being the same color now. I read online people can have a hook effect where if your hcg is high enough, the test actually overloads and looks lighter. Anyone??