GA pilot reported a momentary loss of aircraft control while on the RNAV 28 approach to C29 airport in IMC conditions.

Narrative

The event occurred while on the RNAV 28 approach into Morey Field (C29). The flight originated from ZZZ under MVFR conditions. I did not file a flight plan. While enroute; ceilings were lower than I expected so I requested; and received; a pop up IFR clearance direct to C29. The flight enroute was uneventful. Upon contact with Madison Approach I requested the RNAV 28 approach into C29 and was told to expect the approach. I received a vector assignment of 050 degrees. At that time I assumed I would receive vectors to the final approach fix and set the GPS (Garmin 530) for vectors to final. I then received an altitude assignment that put me into actual IMC conditions. I was then approved for the RNAV 29 approach via the IAF EXIDE. This was my first time flying in the area and I had to confirm the IAF name. I received a vector to the IAF and while updating the GPS route I entered an unusual attitude. Once I recovered from the unusual attitude I already passed the IAF and instead of flying the appropriate approach via a course reversal I immediately turned inbound which took me out of the protected airspace and close to Madison (MSN). I then continued the approach without incident and cancelled my IFR flight plan in the air.