possible low HCG

Hi guys I've had a 28 day cycle and I'm in my early twenties. Been trying to conceive for the first time in May and I missed my period completely this would be my second child but I barley feel pregnant and I took a test about a 4 days after my period was due and negative! It was advanced clear blue ! Anyone ever maybe had low hcg? I'll test again in 2 days in the morning and see