1.是：I don't know what I should do.
2.
1）如果只是一个简单的特殊疑问句,它要求采用倒装结构,应该是：
What should I do?
2）但是此句中,what should I do不是单独的句子,而是做主句谓语动词know的宾语从句,而从句的结构一律是：疑问词/引导词 + 陈述句（句序）.
所以一定要变成：I don't know what I should do.
what就是疑问词/引导词,而I should do才是陈述句序（即主谓宾等结构按序排列）,should I do不是陈述句的句序.
3）再如：
简单的特殊疑问句：How old is he?
它变成从句是：I don't know how old he is.