I agree with margypops that you should get your baby checked out by the doctor. It sounds like he/she may have a respiratory infection and as he/she is wheezing it may also be in the lungs.
At 6 months it is likely that the baby is teething and it is very common for babies to be unwell when their teeth are coming though.
You can put a bowl of hot water in the baby's room with some Vick or other menthol drops in it to help with the breathing. Make sure that it is well out of the baby's reach. You can buy Vick specially for young children and this can be rubbed on the back and chest. There are plug-ins that have menthol vapours to help with breathing. Carvol drops that are placed on the edge of a pillow or as directed to help unblock any congestion.
As you wrote on the 20th I do hope that the baby is much better now.
Has he been checked out at the doctors ..it sounds like a respiratory issue ,and he will need some meds to help him. there is a virus going round .its not dangerous .So get him checked out ..let us know how he is doing ..