While praying Zuhur prayer I doubted whether it was the third or fourth Rakat. I considered it the third and offered another Rakat after that. Was my prayer valid?
If you doubt between third and forth Rak'ats, you must take it as fourth then pray one Rak'at of Salat al-Ehtiyat which is performed immediately after Salaam, by reciting Sura Al-Hamd only, then Rokoo' and two Sajdas, then Tashahhud and Salaam.
Wassalam.