This question has been put several times and several times, answer was given. Ram, in his heart and mind did not suspect Sita and Sita very well knows this. Consider this scenario "Ram did not suspect Sita and took her happily". What would have happened then? People like balakumaran would say that Ram is a stupid gullible fellow to believe Sita and Sita is not a chaste woman because she was under Ravan's custody for some time.
Now what happened? Ram put the complete blame on himself and lifted Sita to the status of a woman who is chaste and leads by example. In fact, Ram had so much love for his wife and took all the useless blame that you morons would put later on himself.
