Stray thoughts of committing shirk

If I was ready to commit a sin even it is shirk, does that mean that I comitted shirk ? Will that sin be shirk if I do it again? If I am doing something with the doubt whether it's shirk or not does that mean I comit shirk ? If I dont stop doing a thing with doubt that it might be shirk .. does that mean am committing shirk ? What can do for over come this ?? Is that mean I comit shirk and is it shirk to do that thing again or have some other way to ask forgiveness and do as normal sin ? Will Allah forgive me if I continue this sin and think as normal sin or will it be considered as shirk if I do these sin ? These are not important than Allah so what should I do ?