Question about my experience so far

I've had the helix syn for maybe 1-2 yr now, using it maybe once a month or two. I've noticed that after I've become sufficiently relaxed/aroused, if I contract my sphincter almost completely I'll feel a sort of jolt and my entire body will spasm involuntarily, originating from the abdomen. I'm wondering if this is from the aneros making contact with the prostate? Would anyone have any advice on where to go from here, how I should use this (ie should I hold it there contracted, or try repeatedly stimulating that area with contractions?). Also, would this mean that the helix syn might be too small/short for me since I have to contract pretty far to get this sensation?

I have yet to experience the super-O yet, right now I'm mostly trying to experiment with do-nothing. So far, no luck yet, though at one point I do remember a sort of warm sensation that seemed to originate from my groin and proceeded in a wave throughout my body (felt a bit like when you get a CT scan and the nurse gives you the IV contrast if anyone has ever experienced that) but this only happened once and almost immediately dissipated, and I haven't been able to recreate it.