Can Pneumonia come back?

My son is almost 18 months. A little over a month ago he had pneumonia. Not even a week after recovering from that and finishing antibiotics, he got strep throat. After 10 days of anitbiotics and breathing treatments because the doc said his lungs didn't sound completely clear...tonight he suddenly gets a 103.3 fever. Its been almost 2 weeks since he got over the strep....but he has never gotten well. He has continued to randomly throw up. He gets to coughing so much he gags and/or vomits. I don't understand why he still randomly pukes. I'm soo tired of cleaning puke. Well today and yesterday I noticed he was burping alot (he never burps), then today the coughing started up again, along with 2 pukes, then this evening the fever struck. I gave him motrin, it went down, but came back when the meds wore off. He is coughing, sounds a little congested too. Im irritated that it's friday now and the doc is closed for the weekend. I'm prepared to go back to the ER if his fever is still spiking tomarrow. Any thoughts on if maybe his pneumonia has come back? Could he just have a common cold? I wouldn't be so concerned...but given he has been sick for over a month now, I wonder, could the fever be indicative of a more serious problem? (of course I will find this out when we go to the doctor, but I would like to hear some opinions)