Low Hcg levels

I noticed that I had a faint positive Thursday night..the next morning it was a little darker on a fmu test...went for bloodwork after work at around 3:30...the next morning (Saturday) the digital test came out positive and the lines on the FR test were even a little darker again...That same day I had very minimal spotting and intermittent cramps after driving for a few hours out of town...Sunday I took a test and it was as pink as the control line but just thinner..digital also said pregnant...I got my hcg levels from Friday and they were at 21...they said that was low..progesterone was at 25 and they said that was perfect...I'm worried about the hcg levels BC last month it was at 25 and I had a miscarriage a few days later ...if the lines are darker is it possible that the bloodwork today will have higher hcg and everything will be alright?