Pregnancy cnfrm/Is it ok. 100%assurance?

Hi, doctor,LMP is 15th Dec   pregnancy check up was done on 18th jan  early morning sample pregna test kit it is +ve ,1 line thickness,1 line thinner found and then checked beta HCG also got 189 miul range for 4th week, which is follow of ranges and confirmed doctor and given course for medicines. While the viability scan is not perfectly visible as the fetus in that scan said who was the scan doctor and suggested checking in next week then it will clearly view on that day so Now my gynaecologist doctor said use medicines upto  15 days then will scan again that day.attached viability scan details and beta HCG test reports for information My queries are 1.when I want to scan again for 100%assurance ?  In 7 days as an informed scan doctor or gynaecologist of 15 days which is good for me 2.Beta HCG test ranges are ok for double confirmation of positiveay be . Please suggest what types of precautions can be followed and my pregnancy is safe for now and later also