Getting Bad Thoughts About Allah and Islam

Asalaam Alaikum everyone,

I have been getting a lot of bad thoughts about Allah and Messenger saww and Islam , I know it's from shaytan and Prophet Muhammad saw said that this is the indication of Imaan in One's heart, but what is worrying me is I get thoughts about what if these aren't from shaytan but I know these thoughts disturb me mentally and my heart sinks everytime I feel so and I do istigfar everytime..