Is a chemical pregnancy a miscarriage?

My doctor told me my hcg numbers didnt double over 2 days but dropped a bit, I am 18 dpo today so he called it a biochemical

pregnancy ..he said I am confirmed as pregnant via blood test but they didn't double.. is it correct to say I am miscarrying or will miscarry soon? i'm not sure the difference between a chemical and miscarriage and he told me i was definitely pregnant ... but that i will prob just discharge anything through a period in the next week or two or it will be like a period.. i'm really sad and just looking to understand more.. would i count this as a pregnancy and miscarriage?