Questions regarding ?maybe? my closest attempt to orgasm

Hey all – first time using any toys. I got an Aneros Syn.
First time I had no idea how this was supposed to be use, I just wanted to play with anal stimulation while masturbating. Then I realized this is something totally different which I was excited to learn!

Yesterday I tried again. I was laying on my side and following the guide of “sucking the toy in” with my anal muscles and then relaxing. After about 5-10 minutes my legs started shaking. Then like my whole body was convulsing, I was breathing super heavy and it was crazy. But I didn’t achieve an orgasm. I felt I was close, but there were “waves” where I would start shaking and feeling this “chain reaction” starting, but then it faded away.

Is this normal? If I kept going would I have had eventually the orgasm from your experiences? I was shocked how fast my legs started shaking and I really hope that this was a good sign I was doing it right!

Thanks and have agreat day:)