This happened about four or five months ago during my schools summer holidays.
My girlfriend and I had been going out for a few months and we started going into each others houses a lot. I'd felt my girlfriend up 'down there' many occasions before, as had she done to me. Although we'd never go any further than a quick feel.
One particular day my girlfriend was kissing me really passionately whilst rubbing her foot up and down my leg. Her hands were all over me and needless to say I got a boner. Her hands gradually moved from my neck to my penis and she unbuttoned my trousers but went no further. Feeling rather sexually frustrated I started to stroke my penis slowly whilst moving my hand down towards her vagina. This was my first time, so I whispered in her ear to show me where she could feel it (I wasn't 100% sure where the clit was) I had intentions of making her orgasm although I wasn't making them known. I slowly moved my fingers up and down her clit until she whispered in my ear asking me to do it faster. I did, and she had one of the best orgasms to date. She spasmed all over the bed and grabbed me tightly around the neck.
She started kissing me again and now started very slowly stroking my penis. I whispered in her ear 'if you do that a little faster, you'll be doing something naughty'. She complied and started jerking me off. After about five minutes her hand started getting really sore. She wasn't the best at jerking off but it was her first time so I wasnt being petty about that. She kneeled up and took off her t-shirt and bra. She stood over me whilst I jerked off in front of her. She stared intently at my penis. I felt so horny and could feel myself getting closer to an orgasm.
My girlfriend lay back down on the bed beside me and started running her hands up and down my body. She was now totally naked apart from a g-string she had put back on when she stood watching me. I could feel her large breasts on my body and she pulled off my t-shirt and started toying with my nipples. She started making panted breathing sounds in me ear as if she were about to orgasm. I was getting really turned on and was so close to coming when she ran her hand down me again and started jerking me off. This time it was sooo good and I could feel my legs starting to shake. She whispered 'cum all over me' and then I turned my body around so I was facing her. She started getting faster, and faster, and faster-until I shot a HUGE load right all over her stomach and beautiful tits.