1. please; if you would; would you mind
どうかゆっくりして行ってくださいね！Please take your time and stay a while!
2. somehow or other; one way or another
3. whether (or not); if
as かどうか
それはどうかわからない。I don't know whether or not that is the case.
4. strange; (something is) wrong; (something is) off
この時の私はどうかしていたのだと思う。I think I must have been out of my mind at that time.