Who are we to tell you this? You are living in the 21st century and you are free to follow any religion, even more than one. Once you put your faith to any religion and don’t contradict the other religions in some way, you can follow multiple religions.
To me all religions are equal and perhaps you should believe that there is a single entity who is called God. But, it is subjective and each religion describes it differently. Suppose, I am a firm believer in Christianity, and after death I encounter the figure from my belief system, such as Jesus Christ and you are a firm believer of Hinduism and believe in reincarnation and karma, and after death you are born again.
Both experiences are seen as equally valid, and one can therefore state that whoever holds this view believes in both religions, but he or she does not necessarily cling to both. There is a quite a bit of debate and variation on polytheistic topics but in my opinion you can follow any religion as long as you don't discriminate people on the basis of their religions and think all religions are same and there is only one God.