HCG levels increased but not doubled

Hello all!

This has been such an emotional roller coaster.

I think I ovulated July 14/ 15.

Spotted a week later with a bit of cramps. Took a pregnancy test July 25, vvvv faint line. The line grew darker since.

Light Spotting the following week and then it got a little more (still not more than a pads worth... not even close)

Called my OB and they sent me to the ER. (Tuesday)

Took my blood and my HCG was 138.

Went back two days later (Thursday) and it was 270.

It didn’t double but increased so they ordered more bloodwork the following Monday.

Monday HCG was 606.

Has anyone experienced this before? Not really a double but an increase?

I am going back tomorrow for yet again another blood sample....