Tried a new position.

Legs flat on the bed works great too!!

Posted by: @bill-bately

Mostly through the years (many!) I’ve been a left side user. I occasionally feel like doing it on my back, but the ending seems elusive and inconclusive. 
Then I remembered a stretching exercise where you’re on your back, knees bent but as low bent as possible with your feet flat on the bed. Not to the point of straining but comfortable. 
This seems to work very well for me. Great access to nips too if you’re so inclined!

My experience is much like yours. I get the best results while on my left side. I can occasionally get pleasure while on my back but sometimes feel that the sensation of the mattress on my buttocks distracts me a bit. Definitely great for the nipple play though which I love!