Low hcg

So I ovulated the 4th of September I believe from my bbt chart but the first day of my LMP was aug 13. I tested positive Saturday. It was faint, but has progressively gotten darker over the past few days and I had a positive on a digital today. Yesterday I had blood drawn and my hcg was only 90. I go tomorrow for a redraw to see if it's doubling but I can't help but to worry.

I took a test this evening and the lines were equally dark so that gives me hope that my tests are progressively getting darker. Any thoughts?