Please help! 美国老土

One week after being interviewed by company A (top company)in west coast, I joined company B in mid-west area. In my fourth week in B, A offered me the job. My wife and me like A a lot because of its reputation in industry, although there is only 10k difference in pay. We don't dare to take A's offer because I barely work for B for a month. We don't know what B will do if we leave at this stage. Meanwhile, we haven't told A that we are already working for B (need to transfer H-1).

We like A, but don't want to hurt B. What do we do?

Thanks!