Aww, normal lang yan mama, lalo na kung may sipon, babies lose weight quickly pag may infection or they're not feeding well kaya parang pumayat agad, but it usually comes back once they feel better na. I'd say monitor kung kumakain pa rin siya normally, at check with your pedia soon lang para sure, especially since first time mo pa lang, para matulog ka ng mahimbing at walang alala. Sending you a tight hug, kapit lang, phase lang ito!