PA-30 Twin Comanche
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 3; Flight Crew Total 575; Flight Crew Type 266
Confusion; Situational Awareness; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem
Human Factors; Procedure
During a solo flight from ZZZ to ZZZ1 I was cleared for the ILS XX into ZZZ1. Not having flown an ILS approach in a while; as I normally chose RNAV approaches; I decided to shoot the ILS. With the autopilot on; I turned to capture the localizer; the bearing pointer never appeared. Tower called on the radio and said that Approach was reporting that I had not captured the localizer. I replied that I thought I had intercepted it; but something did not seem right and requested to fly the missed approach. I was then asked to change frequencies back to Approach Control. I was given a heading and was leveling off. I then turned the heading bug and turned off the GPSS function on the autopilot. My focus then went to why the GPS did not display the bearing pointer for the localizer. At some point I realized that I was in what I thought was an unusual attitude; and maneuvered to level the wings and raise the nose to stop the descent. Still not knowing why or how the autopilot turned off. Approach then contacted me about my heading and altitude which resulted in my focusing on whether the autopilot was on or not and; another pitch up and slight bank occurred. At this time I had become uneasy and unsure of myself and asked for an easterly heading. I was given the heading and an altitude that would put me on top of the clouds. Once I broke out of the clouds I took a deep breath; confirmed the autopilot and GPS were set up correctly and asked to return to ZZZ.Once on the ground and given time to decompress; with some review of the GPS system; I realized that I had not flipped the localizer frequency during the initial approach which started the issues. Subsequently my focus was diverted and I stopped doing [the] basic job of scanning. I still have not figured out what the issue with the autopilot was; whether it disconnected on its own or if I hit the disconnect button on the yoke inadvertently.
PA-30 pilot reported not being able to intercept the localizer and thought he had GPS equipment problems.  Pilot eventually realized he had not flipped the localizer frequency to correct position.