It sounds as if your baby has congestive heart failure now. Please seek a pediatric cardiologist at a major pediatric center to help your infant ASAP. Babies can withstand cardiac stress for some time, but will crash! I'm not trying to scare you, but I promise I have experience with this as a healthcare provider and pediatrician. Your baby needs an echocardiograph now, and maybe other tests, and then perhaps medication until surgery, if that is needed.