OP, like you I'm 35 and my mum is 65.
My earliest memory of talking to my mum about sex was when I was 4 and I said, "Mummy, why does Elliott (the boy next door) have a tail and I don't?" (We'd been in the paddling pool together) She responded: "Because boys have XY chromosomes and girls have XX." (??!)
A couple of years later an explanation followed about how babies were made which involved the man and the woman taking their clothes off and the man passing a seed to the woman. I envisaged them standing on opposite sides of the room and the man squeezing his penis until an apple pip popped out. He then passed it hastily to the woman, who put it inside her, before its magical powers depleted. I remember thinking: I'm never going to be able to make a baby, there's NO WAY I'm taking my clothes off in front of a man!
When I was 10, I recall coming home from school and saying: "Mum, you never told me people did baby-making for FUN as well." She said "who told you that?!" and she was mortified.
She then gave me an Usborne guide to growing up (like others on this thread), which explained about pubic hair, etc, but this didn't make me any less embarrassed when I started growing some myself - I was an early developer and used to painstakingly tweeze every hair from my armpits and groin because I didn't want to be different from the other girls in my class.
Shortly after that the school nurse came to talk to us about periods - she passed round a sanitary towel, and talked about menstruation, which I got confused with masturbation and thought was terribly rude. In my first year in secondary school I started my period and approached my mum. She gave me a tampon, but I followed the nurse's instructions and just put it in my knickers like I would the sanitary towel and of course it didn't work, I was so confused. I eventually found out where I was going wrong through Just 17 magazine.
I got my first serious boyfriend when i was 14. He was 16, but he was a devout Christian, so we were together for at least a year before sex was on the agenda. I remember deliberating in my diary about whether we should "do it." Of course, my mum read it and went ballistic and phoned the boy's parents, because I was still only 15. I was promptly grounded and I hated my mum for invading my privacy...I did finally lose my virginity to the same boy when I was 16, but neither of us knew where to get our hands on any protection, so I subsequently spent a very anxious 24 hours traipsing around family planning clinics until I could find someone who was willing to give me the morning after pill. We split up shortly after that, because "might I be pregnant, what have I done?" played so heavily on my mind, it overshadowed everything.
I wish I had been able to talk to my mum about contraception, but she had a very "moral" stance when it came to sex, and I couldn't afford to let her know that I was sexually active. She and my dad have only ever slept with each other and while I think that's commendable because they're still utterly devoted to each other 45 years on, life doesn't always work out so neatly. When she did learn that I wasn't a virgin, her gut reaction was to call me a slag :-( Of course that made me rebel against her and sleep with a whole host of inappropriate men in my late teens / early twenties.
To this day, I know that sex is pretty much an off-limits subject with my mum. However, in recent years she's worked in a shop with several women in their 20s and I think its opened her eyes to just how open the younger generation are in comparison and she seems to be a little less guarded these days. She point blank refuses to learn how to use the internet, but I do sometimes wonder what she'd think if she came on a forum like this and saw how open people were with each other!
I'm not sure if I've answered your question OP, but I've certainly had a trip down memory lane....