Help! I’ve had the first sex talk with my 7 year old!

Help! I’ve had the first sex talk with my 7 year old!
A few days ago my husband was reading out my stars, it mentioned the words money and SEX!!!. Our DS 7 chimed in with a little giggle and our conversation went something like this:
DS 7: sex, why did you say that?
Me: why’s that?
DS 7: giggles and whispers ‘sex’
Me: Yes, do you know what that is?
DS 7: jumps up and does a hip thrusting dance!!!!
Me: Dancing?
DS 7: No……..It makes a baby.
Me: yes that is right, that is how mum and dad made you as a baby… just like our guinea pigs. When a boy guinea pig and a girl guinea pig breed they make a baby, it is the same for mums and dads, but we call it sex.
DS 7: oh no you didn’t sex!
And that is where the conversation ended………since then I have wondered if I could have said or done something different. I must admit, I certainly didn’t expect to be having the birds and the bees conversation with my 7 YEAR OLD! I mean where on earth did he hear about it? How does he even know about it? I remember when I was 7 I was playing with dolls and dress-ups! I feel so completely unprepared………..HELP!?!?
I guess right now I am just waiting for my next opportunity to talk to him again. I don’t want him to misunderstand what sex is and I don’t want him to think sex is something he can’t ask questions about. Jersey wrote a blog post a while back about how to prepare yourself for the birds and the bees talk and I think I will go and have a read of it again, see if I missed anything, or if I’m just in shock!
I’d love to hear if you have any helpful tips or advice? If you’ve had this initial conversation how did it go?
Help! I’ve had the first sex talk with my 7 year old!