I second physiobob... your xrays look perfectly ok - your Wikipedia reference-linkSIJ joint margins are clear and not sclerotic or notably inflamed/adhesed (atlhough i am not a radiologist) - they look fine to me. You need a full assessment with a physio who can assess your pelvis and lumbar spine and your bike set up. You may also consider hip flexor length and glute med strength as a power imbalance causing pelvis issues, and core strength as an exercise based therapy. Cycling is bike set up, posture, strength, length and technique.

Cheers,
msk101