Thanks ladys this really has helped me.
I've had each one 5 years apart and I still feel guilty on #3. When my son was born I gave my older daughter a doll and told her that it was from the new baby to her. She completely believed it and thought it was so nice of the new baby...
My kids adjusted just fine. They are all about 21 to 36 months apart. They barely even noticed the new kid both times! I tried not to make it a big deal for them, just told then a new baby would be coming and that was about it. No sibling classes or any of that junk! We just introduced the new baby and went on with breakfast as usual. No big deal! I let them help by bringing me diapers, blankets, pacifiers, and "checking on baby". Your little one will be fine, just don't overdramatize the situation and he may not even notice the new kid!
I waited 11yrs before I getting pregnant again. With my experience it was very difficult because she voiced her opinion. And it was very hard when I told her she was going to be a sister. She was very jealous saying she was suppose to be the only child. And she started acting up and everything. Luckily i told her early in my pregnancy, because now I'm 33wks and she is excited. I think your son will probably act up a bit and be jealous too. From my other friends who have children said that their kids would start acting like babies because they see the baby crying and being held and they get jealous. But i think I would have been able to deal with that better then a 11yr old acting up as bad as she did. Anyways good luck. Sorry I couldn't be any help, but i reassure you that it'll be easier to deal with then an older child.
I am pregnant with baby number 4 and still worried about similar things :) I found that you get extremely overprotective with the new baby... maybe even frustrated with other kids if they want to do anything with the baby. But after 2 or 3 weeks it all just get into places :)
What you are concerned about is totally normal and probably won't completely subside until your new bundle arrives. I remember when we were pregnant with our second I was terrified my first would feel like he was getting less love or act out. As it turned out he loved him. They are 2 years 17 days apart and best friends.