My son is 7 weeks old and for the last two days vomits up shortly after breastfeeding (usually 10-20mins afterwards). its quite a large amount. ?

Common issue: All infants may develop some backwash of their stomach contents up the swallow tube. It can start out mild & seems to peak around 2-3 months when they have more muscle tone. If they are thriving is spite of it all you can ignore it. Sometimes leaving them upright for 1/2 hour or so after feeds helps (gravity). If the kid develops pain/fussiness that suggest acid burn your doc may prescribe meds.