Hcg levels too low ?

Okay ladies im 11 days late iv done 3 home tests first response and a clear blue digital saying im preg ..my doc has done 4 tests barely faint lines and negative ! She done my bloods at 3 days late ..hcg was 63 she did them yesterday 10 days late hçģ was 154 ..she said i need to have them done again in 4 days.she said she is happy with them but they could be higher...im worried...are my levels too low ???