sweetie, the scan alone is only 70% accurate, which means that there's 30% chance that the baby is alright. and sometimes there could be mis-judgement. the blood test alone is 80%. combined both together and with your current age, the accuracy is at 90%. but the overall result would not give you a confirm answer too. it'll only indicate whether you are high risk or low risk category and low risk is not equal to NO RISK. just wait for the blood test and see how. maybe all will turn out to be alright without going for invasive test. if not, there's still anmio with about 0.5% to 1% risk and with current technology, your pregnancy would be in good hands.
i know it's difficult to face it. i've been through some thinking when my gynae counselled me on my ultimate intention of going through the DS test. for me, i questioned myself if i'm willing and prepared to go accept a DS child and my answer is no. ultimately, you have to ask yourself whether you're willing to keep the baby if the amnio turns out negative. there's a lot of factors to consider such as future living expenses, medical expenses, caregiver, etc. but in the meantime, just take one step at a time.