Can only have an orgasm when on top

I have had three orgasms in my life, two were symontanious and that was with one of my ex boyfriends and I also squirted then and the other I'm not too sure about, I was lying on my back with a pillow propping me slightly upwards and my bf was licking my clit and near the end I couldn't stop myself from wanting to hold his wrists that were on my hips and I had a powerful tickle after my hips wouldn't stop fidgeting around and it felt like a realy great orgasm but from the first time I experienced it two years ago I remember it to be different, this time the feeling of happiness faded a lot quicker even though it was a longer pleasure, afterwards it was like it didn't happen when the first time I was smiling and throbbing down there for 2 days and this time I also didn't squirt when the first time I came with a gush sound lol as soon as I came that's what it sounded like, saying the word "gush" . And i would please like to know why I find it so hard to climax and have an orgasm? And I would like to know what was it that was happening with those two different times why was the first one soooo much better but this one only more restless and twitchy to feel myself !! Please help !!