Light aircraft pilot reported descending below Minimum Vectoring Altitude on approach to 3GM; citing clearance confusion and weather conditions as contributing.

Narrative

I was in the final stages of my IFR flight from ZZZ to 3GM. I was making an RNAV approach to Runway 27 3GM. Conditions were heavy IFR with fog; clouds; rain and moderate turbulence.During the final phase of the approach the controller said that I had descended below the Minimum Vectoring Altitude during the approach by going down to 2;100 MSL versus the 2;700 minimum. I did reach this altitude but not intentionally but due to the turbulence and trying to maintain control of the aircraft. A contributing factor was that I was distracted by trying to locate my position on the chart because the controller gave me vectors to two approach fixes with similar names on the same approach. The fixes were named 'FIVLO' the IAF; and 'CIRBO' the FAF. I was having a difficult time understanding which fix he was referring to because of the heavy rain; transmission static and turbulence trying to read the chart. During the approach I did unintentionally descend to 2;100 MSL but did climb back to 2;700 MSL when I regained control of the conditions. As I finished the approach the controller advised me of the violation and gave me the phone number of Great Lakes Center to call. Immediately after landing I called and supplied my name; address and phone number and pilot certificate number to them. They said that I would be contacted if they needed any further information.I feel that having two approach fixes with very similar names; on the same approach should be reviewed and corrected as it definitely contributed to my accidental and unintentional violation.