Have a look through the P-spottig thread theres lots of good tips in there.
Anatomy is not standard, so finding a toy that hits the p spot can be a bit hit or miss. It does kind of sound like you found it though from what ive read on the thread (although, Im female so cant try p spotting. Sounds fun though)
Anyway ask the guys on there, they know their stuff
By the sound of it though its kind of something you have to work at, like g spot orgasms.
Either way, sounds like you had fun and got the plug in comfortably, so thats great 
You have to kind of adjust to anal anyway, its not an instantly pleasurable as your brain doesnt know what to do with the new sensations so usually feels odd to begin with, so id keep at it.
All else fails you can always return it. Its 100days from time of purchase now