Involuntary contractions happens on its own without me manually clench my muscle.

Last night, involuntary contractions happens on its own. I didnt manually clench my pc muscle or my spinchter muscle at all last night. I totally didnt do anything except focusing on being relax and calm, enjoying every little pressure or pleasureble feeling coming from my penis and being horny by fantasizing about my girl. It totally works for me. I even didnt play with my nipple at all and my penis keep on being hard and feeling dripping with pre cum. I can feel it drip from the tip of my penis and it feels so good. At one time, my ass clenched very hard on its own. I thought it gonna poke a hole through my anal wall but instead i feel something coming on my penis and it is pre cum. Not ejaculation last night, only dry orgasm but still it is very good session. My aneros being clenched or squeeze very hard involuntary, it feels like my prostate being stroke slowly and it comes waves after waves. Its not rapid clenching movement but as i keep relaxing and focus, it comes again later. So good to share this in this sub. Feels very horny and cannot wait for my next session.