Hi A.,
I can TOTALLY relate to your situation!!!
I had my second daughter, Rylee, on 2/4/10 and my first daughter, Marlee, was 23 months old. Much like your son, Marlee was our universe. It was extremely difficult at first, and I felt like I was always nursing Rylee. Marlee would come over and try to cover me up and say, "Mommy, put that away." Kinda funny now, but I still feel like you do - that aching part of me not wanting my older child to grow up and become so independent, so soon, because I am not able to spend more time playing with her.
I recently stopped nursing Rylee - well, she is almost 8 months now, and started supplementing with formula at 2 months. It killed me, because Marlee was strictly nursed until she turned one year and weaned when she was 14 months - it was just her preference and I was happy to oblige...lol I had to remember that no two kids are alike...and formula babies live long, healthy lives too...
Now, also like you, I feel like Rylee did not get the attention Marlee got at this age. Rylee can fall asleep on her own, and is almost walking on her own...crazy early. I held Marlee ALL the time her first year, and she didn't walk until 14 months. I loved the connection I felt with her - like I could give her all of me.
My mother in law, of all people, put it in perspective for me...
Marlee had mom's love and dad's love. Rylee has mom's love, dad's love, AND her sister's love, nd Marlee is adding her new sister's love. Siblings, no matter how much they pick on each other, have a bond that cannot compare to any other, much like the bond we felt when our first little one's were born. Rylee knows no different - she has three people that love her and isn't mentally comparing and thinking, well, ya know, mom spent more time with Marlee when she was my age...a lot of it is in our head in trying to keep things fair.
As far as your son's behavior, it may take a while. Marlee and Rylee play and laugh together all the time, but Marlee still has her melt downs...she is two and a half after all. Not all of his behavior is from his sister; it is partly from his age. I do notice that as Rylee is able to move around more, and actually 'play' more with Marlee, Marlee has calmed down a bit. At first, she was like - what is this thing you brought into my house - she doesn't play with me, so she must not like me. Now, she is realizing that she is still loved as much if not more so, and her sister can do more and more with her.
Hang in there! Stay firm with your son - hitting is also a normal behavior for his age - not acceptable, just normal...lol (Marlee is a kicker). It is much easier for us now, but everyday brings a new scenario to face and deal with.
And yes, the guilty feeling does go away...it drifts back every once in a while, but it is never as hard to deal with as those first few weeks...When things settle down, and schedules fall into place, you will find that amazing bond/connection with BOTH children and husband and your son will come to realize that he still holds that special place in your hearts!!!
All the best,
L.