dog causing fights?

we had a dog before my son came my husband and I thought a lot but I just thought that was that. we decide to put the dog in a new home after the baby came couldn't handle the stress between a high energetic dog and a newborn baby. 6 months later we got the opportunity to have that same dog back and decided to do so. during that six months without him my husband and I almost never fought and if we did it was just little disagreements suddenly now that the dog is back it seems real fighting like cats and dogs what is wrong? Is it possible a dog can cause this. what should I do?