You're going to have to give more specifics to get more helpful advice. Do you get multiple bands when you use genomic DNA as a template? That means that your primers are not specific and you will need to design new ones.
Do you get multiple bands when you are using cDNA as a template? You may have genomic DNA contamination. Run all the appropriate controls (gDNA, cDNA, water).
If you are absolutely certain that you do not have gDNA contamination, then you either have splicing variants, multiple alleles and/or closely-related genes that give almost-the-same size gDNA PCR products, but different size cDNA. Clone and sequence your PCR bands.