Don't laugh. I'm 31 - had just two long term relationships - both of which were boring in bed with 99% of sex missionary with the very rare attempt at sex from behind. I've had no one night stands or short relationships, FWB etc so my sexual experience is pretty shit.
But I've not really enjoyed sex before so I didn't care, it was just a case of lie back and hope they get it over with quickly 
But - new relationship, I'm slightly head over heels with this guy and for once in my life, I enjoy sex with him. We've slept together 3 times - everytime was missionary.
Last night we were in bed, he was massaging my back and I was laid on my stomach, his sat over my back and I think something ticked in his head and as we went to have sex, he asked me to stay on my belly. Well it was a really awkard affair, it kept slipping out, I didn't understand what he was asking me to do when he asked me to move slightly - in the end he lost his erection and we had to give up
I was laying there next to him thinking "I can't let the night end like this when I'm not going to be seeing him again for two weeks (different thread) and so I initiated sex again and climbed on top of him. THAT worked well
and I quite enjoyed it.
Still confused about the 'from behind' thing though, why wouldn't it work? am I weird?
And do I tell him that I'm inexperienced so he can show me/explain to me what he wants or just keep quiet and learn as I go along? (possibly making a tit of myself in the process)
He's 10 years older than me, likes sex and can go all night... I don't want sex to be the thing that shows us apart!