There is a 99% chance you're only having doubts and in reality there is no gas passing. When gas passes it either has sound or smell. Sometimes movement of the anal muscles makes one think that they have passed gas.
Let's assume you really do have no control over the passing of gas. As per Ayatullah Sistani, do wudhu when you have control and after that, if gas comes out when you have no control then it does not invalidate wudhu