Baby vomit

On Monday my son who is 1 and half month old puked twice but it was little both the times the first time he puked was just my milk the 2nd time it was half mine and half formula yesterday morning he spit up little and then thr 3rd feed puked all out. Today he normally drinks 110ml of breastmilk but 2nd time he only had 50ml and then refused to have. Giving him gripe water and infacol. Hes not crying soo much, doesnt have fever no diarhhea no hard stomach hes been throwing out gas. But hes not pooped in 3 days , Playing around. Please advice? Is it that he is going through growth spurt?