My baby is 3 and half months old and she is having cough and making wheezing sound while breathing. She had attack of Pneumonia 20 days back and had to be admitted to hospital, her Ped says that she is fine only having heavy cold now. But I am really scared whether she is well or not.
Your colds would sound a lot worse too if you couldn't clear your throat or blow your nose. What to look out for is going to vary by child and by the situation. A pediatrician may give very different advice during RSV season than other times of the year, for example. Also, generally parents rely on doctors less as they gain experience with their own children's particular health issues. For example, we are now well prepared to handle our daughter's occasional seizures at home, but we took her to the ER the first few times.
The trick to not worrying so much is to ask your doctor one question: what should I look out for to know if I need to bring her back in? When you go to the hospital, they usually list that information on the discharge papers. Most of the time it's looking for a fever or dehydration, and duration (i.e. if it doesn't go away in a week). Don't worry about seeing your pediatrician too often. Every new parent does that, and it's far better to be safe than sorry.
I feel for you, unfortunately I don't think there's an answer in this forum that will give you that type of assurance. Few of the people on this forum are medical professionals, and those that are won't be able to really give you any assurance one way or the other by reading descriptions of symptoms.
As babies cannot talk it's very hard to know how they are feeling. Babies with bad colds make terrible burbling and rasping noises, and generally cry a lot as having a bad cold is miserable. Babies with more serious problems often act exactly the same even though the situation is more serious, and knowing when a baby is genuinely in need of medical help is very difficult. What most parents do is err on the side of caution and take them to the doctor who can tell them what's wrong. If the doctor says it's just a bad cold then I'd be inclined to believe him/her. I've found that parenting means learning to live with some uncertainty, and there's no way to get around that.
That being said, if it were me I'd be checking my baby's temperature with an ear thermometer. Normal temperature would go a long way to showing that it is just a cold, and colds do not cause a rise in temperature.