LOW-TIME C172RG PLT ON VFR FLT FOLLOWING CAUSED AIRBORNE CONFLICTION WITH A B737 ON APCH TO CVG.

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UNABLE TO MAINTAIN VFR AT AN ASSIGNED MINIMUM ALT; I CONTINUED A DSCNT IN FRONT OF THE PATH OF A B737 ACCORDING TO ATC. ATC DID NOT PROVIDE DETAIL OF MISS DISTANCE OR IF ANY ACTION WAS REQUIRED BY THE B737. I DID NOT OBSERVE THE B737. WHILE ENRTE; I WAS ON FLT FOLLOWING VFR AT 10500 FT. AT 40 NM WSW OF ISZ; I WAS IN CONTACT WITH CINCINNATI APCH WHO INDICATED 'ALT YOUR DISCRETION' AND I BEGAN A DSCNT. ALTHOUGH LUK RPTED VISIBILITY OF 5 NM AND CLR; THERE WERE MANY CLOUDS IN THE AREA TO APPROX 8000 FT. I SELECTED WHAT APPEARED TO BE A LARGE HOLE ALONG MY PATH OF FLT AND BEGAN TO STEEPEN MY DSCNT. AT ABOUT THIS TIME; I WAS CONTACTED TO MAINTAIN ALT AT OR ABOVE 4500 FT WHICH I ACKNOWLEDGED. UPON APCHING 4500 FT; I REALIZED CLOUDS CONTINUED WELL BELOW THIS LEVEL AND IT WOULD BE IMPOSSIBLE TO LEVEL OFF AND MAINTAIN VFR. I CONTACTED ATC WHILE CONTINUING DSCNT (150 KIAS; APPROX 1200 FPM). ATC INDICATED THAT THEY WOULD APPRECIATE IT IF I WOULD INFORM THEM SOONER NEXT TIME; ADDING THAT I HAD DSNDED IN FRONT OF THE FLT PATH OF A B737 ON APCH. NO ADDITIONAL INFO ABOUT THE MISS WAS CONVEYED. AT THAT TIME RADAR SVCS WERE TERMINATED. I FAILED TO OBTAIN WX INFO ABOUT CLOUD CEILINGS BEFORE BEGINNING DSCNT. I MISTAKENLY ASSUMED ATC'S ALT REQUEST IMPLIED CEILINGS AND VFR CONDITIONS AT THAT ALT. I MADE A POOR SELECTION OF DSCNT AREA; RESULTING IN AGGRESSIVE DSCNT PROFILE; AND ACCEPTING ALT MINIMUM WITHOUT KNOWING IF IT COULD BE COMPLIED WITH.