Must I repeat a prayer if I doubt its performance, especially when combining more than one prayer?

A person afflicted with whispers [waswas] should turn away from them and not pay them any mind. So, if you experience a whisper about a particular prayer—whether you performed it or not—abandon this whisper and disregard it. Assume that you have prayed, unless you are certain that you have not prayed it, in which case you are required to make it up.