Mobizox is the brand name. It contains three medicines: diclofenac, paracetamol and chlorzoxazone. It is highly unlikely that you would be allergic to paracetamol; however you could be allergic to diclofenac or chlorzoxazone.
Mobizox is an irrational combination. Such a combination is not allowed to be sold in any advanced or western country. If at all three medicines are required, then they should be prescribed separately so that their side effects can be monitored and dose of individual medicine tailored to meet specific requirement.
It is also essential that a correct diagnosis be made. Since your pain is related to eating and drinking, there is a possibility that your food pipe may be inflamed leading to acidity. Generally such disorder causes pain on the front side of the chest but it can also cause pain on the backside. If so, then taking Mobizox, even if tolerated, would be counterproductive since it increases acidity.