From pleasure to worry

I'm sitting here rather worried.

I bought an aneros (helix, I think) about two years ago. Tried it a few times but gave up. For two reasons:

1. The pleasure which I got from it was no different from pleasure I was able to generate without the device by visualising my prostate being stimulated and contracting my pelvic floor muscles.

2. I got worried about the whole idea of the male MMO/tantra/taoist sex etc because of the bad things I have heard about 'kundalini syndrome' - which I understand to be a problem with multiple symptoms caused by sexual energy being stored in the head.

I have just attempted lying on my fron, contracting the pelvic floor muscle and visualising my prostate being simulated. It was the most pleasurable session that I have had doing this. At one point, my pelvic floor muscle contracted involuntarily and I had pleasurable sensations over my entire body - like an orgasm.

I would be euphoric, but after I got up, my head moved downwards involuntarily. I feel there is 'energy' moving around my body and especially in my head. It is unpleasant.

Is this natural, or is it something to be worried about?