CHICAGO – Rep. Jesse Jackson Jr., a once-rising political star who has been on a months-long mysterious medical leave for bipolar disorder while facing separate federal investigations, resigned from Congress on Wednesday, citing his health problems.

Jackson’s resignation, just two weeks after voters re-elected him to a ninth full term, comes amid a House Ethics Committee investigation into his dealings with imprisoned ex-Illinois Gov. Rod Blagojevich and reports of a new federal probe into possible misuse of campaign money.

In his resignation letter to House Speaker John Boehner, Jackson admits “my share of mistakes” and, for the first time, publicly acknowledges that he is the subject of an ongoing federal investigation.