1) how can pragnent women do sijda when she feel pain 2)women feel soffocation when she wear heejab

like to ask that my wife is pregnant and she could not be able to bow her head in Sijda in Sallat so as she said she feel pain if she tried to do Sijda so she just bow her head in order to do sijda. is her salat still valid ? or there is some other way she should apply in order to complete her salat properly. 2) my wife is a good practicing of Islam but she find Heejab very difficult to wear. she said that when she tried it (Heejab) its very difficult for her to take breath. also guide me what should I do because I feel very ashamed while moving in markets with my wife and every body is looking at her and shall I force her to take Heejab ?. thanks for your time and concern.