Help Me - Technique? Do I Suck?

Alright friends, I'm about to lose it.

I've been playing drums for 20 years, and I'd say I'm at least "intermediate" to "advanced". Played many jazz gigs, many contemporary worship gigs, hard rock gigs, etc.

But this one thing is absolutely killing me.

I cannot, for the life of me, figure out the proper technique for single pedal, fast 8th notes. (8th notes on every beat, except 2 and 4, where the snare is)

I immediately get pain in my hip flexor/groin. I am trying to hone in on exactly how to have my heel up/floating, but when I move to that position, I naturally put the beater into the BD head.

So to compensate/start the beat, I have to "engage" my quad, which immediately sets the whole thing off - I can't consistently get the rhythm of the (+ 3 +, + 1 +) , so I overcompensate MORE, which causes even more pain in my hip flexor.

I have tried spring tension, batter angle, seat height...

What am I missing? Do I suck? I have such a mental block about this right now I'm close to just saying "F" it, but I know someone out there can help. Please!?

--To further clarify - I don't feel like it's simply repetition - the pain is a signal to me that I'm "off" somewhere and need to be doing this with a different technique.

BPM: I am fairly comfortable around 120-130, but 135 is where I start to lose it - or my leg starts to feel like it's compensating or starting to work.