Baby cough, when to visit doctor

She's 3 weeks old in about 2 hours. But today and maybe late yesterday she's developed a little cough here and there she coughs maybe 10 times a day but also sounds a little congested, she's spit up more yesterday and today than normal as well. On Friday the Dr said gripe water and we started that just a 1/2 tsp once a day. She's breastfeed and I've been taking things out of my diet to see if any of those have affected her stomach. So that might account for the spit up but still unsure with that cough