Advice and Help Please

To whomever reads this I ask for your help.

Okay pretty much everyone of my stories have a sex scene or scenes in it. I think I'm a pretty weak sex scene writer. Even though my readers and friends like it saying things like:
"That was hot."
"That was really steamy."

And so on I think my sex scenes could be better. I also feel like I write them too quick and it's over too fast. Especially when I drag chemistry and sexual tension between two characters for a while and take long to get to a sex scene. Like I said its over so fast that when I go back to read it I just hate it and kick myself for it.

So what would you suggest to do or write to make them better, longer, and more satisfying to not only to my readers but to me?

I'd greatly appreciate any advice and all suggestions.