Convinced I’m going to miscarry

Well gotta great implant dip 9/10dpo and a spike 10/11 dpo. Got First positive pregnancy test 12dpo , 13dpo darker and 14dpo darker and a pos frer digital 13dpo. 15/16 dpo I had my blood draw (Thursday) dr called 8am to say confirmed pregnant ... so

I asked what was my level and she said 21... well I had a CP in dec 2017 and my 18dpo was hcg 7... so already better .... but I tested on a Walmart cheapie this afternoon and it was faint . The dr office did not seem concerned at all this morning and said he wants u to repeat in 1 week to make sure it goes up, but why wait a week? And should I just prepare to miscarry again . I will literally just cry.