Advice from males and females for my 7 year old?

Ok so we have this kitten/cat well he's about to be one year old in like may but we think he's in heat. Actually he probably is. He's been acting weird the last few days and I just couldn't figure it out but I think he just figured out the feeling of sexuality. I don't know if he's done anything, he's a cat.
So lately the cat has been coming to our room like usual, he sleeps with my son and trying to get comfortable in my son's bed but it seems like he never gets it right because he keep clawing at my son's blankets. Well he was doing that tonight and well I had told my son after reading to get under both covers to go to sleep because he had been reading with me in mine. And the cat wasn't all to thrilled that he was losing his spot to his keeper. I went over to move the kitty and picked him up and kitty wasn't to happy.  I looked down on him (not to be a pervert) and his little penis was sticking out. He's, I guess, feeling different textures... Mmm curious cat!
I was hoping my son didn't see it but how could he not the cat's bottom was looking straight to him by accident. Well I didn't know what I was going to see either. We've never had a big male cat.. Then after a few moments it hits my 7 yr old and he says, "Eww, was that the cat's pee pees?" and I said I wasn't sure and then he was like "Yea, it was. Was he peeing on my bed?" And I said, "No, it's fine just cover your self" I took the kitty out of the room and closed the door.
And then my son says this...
"When I dream and I think of Rosale my pee pees stands up too." And I looked at him in (not disbelief but more a "Did you really just  say this?") and all she says, "Really!"
He's 7 and we've never really talked much about sexuality I mean he's freaking 7. I'm a mom. I once told my dad to speak to him but he's too old fashion. I know he's little an curious but he's already liking the feeling of touching himself. He says it tickles and he giggles.

Ok, Moms what would you say? Or how would you bring it up?

Ok, Guys I know nothing about the guy's reproductive organ well you know what I mean. What can I tell my son. I'm the only person my son has had until recently (I've always mainly been his mom and dad) and he's young and confines in me a lot. how can I guide him? What do I do? He's my 7 yr old baby. I'm not going to smother him but I do feel unsure. I wasn't expecting this for quite some time more. Especially the thinking about a girls makes him feel a certain way already.

OH God 28 crept up

My Birthday was monday ... yay, right?!! RIGHT?! Well it didn't feel like yay... I felt like i was 13 all over again and it felt like the worst day of my life. I felt like I was the loneliest person alive. Unlike when I was 13 there was no people so crying was not noticed. I ended up falling asleep with a headache after helping my son finish his homework. It was fine and dandy but sometimes we just feel different on different days. Don't ask me how I feel right at this moment because if I felt better you bet you niceness I would be writing a happy post which I have some to write, I just don't have motivation to write..

That song "Lonely Day" by System of a Down felt more happy than how I was feeling.

I guess it made it ok to be in my room alone and just let it out. It's suppose to make me feel better. And I suppose all those nice "Happy Birthdays" I was getting on facebook were nice yet I was in my room still. I remembering being surround by friends in college and having people to hang out and people would be there for you but then I remembered oh yea, I'm a loner why would anyone really remember me. Then again a loser at 28. I feel like such a failure. I'm suppose to have everything together and nothing is put together. I don't know where I'm going, I don't have any dreams anymore. I can't change anything. I can't go back to school and doing anything right about now sounds better than not doing anything. I just want/ need that part of my life to fall in place so I can be more supportive and upset in a different way. But, I'd be mad but I at least would have my spending my money. I wouldn't be stuck in my room all day trying to fill out apps and never get calls. I don't think my resume is that bad. But, obviously no one wants me. and it makes me sad.

Ok, I feel better for today. But, it still sucks to be 28...  I hope I can dream again and get my life into feeling positive. It's definiely the type of feelings I want to show my son. I want him to feel hopeful about the future and going to school but after my experience I feel I can't give him that... I will try to. But, besides my negativity I hope 2013 is a good year. I pray.