Getting intense, then nothing?

Newbie here, using the Progasm for several weeks. Have been feeling more and more each time I use it, but after one pretty intense sessions, it seems like I'm not feeling anything anymore.

Better Explanation:

Had a session last Sunday that was the best I've seen so far. Everything was pretty intense down below, throbbing, a few involuntary contractions. Had what I would call an 'almost orgasm', heart was thumping so hard at one point it actually spooked me a bit, intense waves were washing over me. Lasted less than a minute, but was very encouraging.

I was very excited for my next session, as things have been progressing nicely for several weeks. But then I have have 2 more sessions since, and it's suddenly almost like I don't even have the thing inserted! Now I'm not even getting very many of the muscle spasms in my legs, that I had been assuming I get when the Progasm makes good contact with my Prostate. I know it's in and pretty much has to be making contact, anyone else experienced this? Why would my body be 'rewiring' and making progress, then suddenly seem like it can't even hardly feel the thing?