Hi Critzz,
your situation is very similar to mine.
I had a fusion 17 years ago, L5-S1.
Sorted my back problems back then and has been great for years since, I've been participating in many sports on a regular basis.
3-4 years ago I started getting left lower back/buttock and groin pain which I immediately assumed was my back.
After many consultations, xrays, an epidural and a back MRI my consultant told me that my fusion looked in excellent condition (some disk degeneration but nothing serious) and that he thought maybe my hip should be looked at.
A simple xrays later and bingo!
Bone one bone in my left hip and yes, my limp was putting pressure on my lower back big time.
I'm now 17 days from my surfacing and the difference is night and day.
No pain whatsoever in my back, buttock or surrounding area.
I have some groin pain and obviously some pain from the trauma of the op, but nothing comparatively speaking.
The groin pain is normal and mainly due to the manipulation during the op and heals over the weeks, as does the operative pain.
I am already walking up to 2 miles per day (on crutches) with hardly any limp. I can also walk (in the house) without any crutches almost normally.
My advice would be get booked in ASAP mate, you won't look back.
Good luck with it all