I'll be honest -going from 1 to 2 IS harder! When they're really small, it can be like willfully throwing yourself in the middle of a tornado! My oldest was an easy baby, and while I did experience a huge transition in life having him, it wasn't as hard on me as it sounds like your first was on you. He was very laid back and a pretty easy baby. I got pregnant again just before his 2nd birthday and had my 2nd son when he was 2.7 years old. He went NUTS when I was about 5 months pregnant. The terrible twos evidently hit full force, built into the terrible 3s and right now I'm just praying for his 5th birthday because I'm hoping some of this baby behavior will subside as he gets older! Wrestling him and a baby was insanity. I look back on the last 2 years and until this past summer -it's all almost a blur of craziness.
To be fair, I also lost my mother last fall (2009) and she was my biggest help in giving me a break from the craziness. My husband is helpful, but there's no one like your mother! Anyway -that didn't help. So many people I knew were in the same boat, and they all kept saying that it got better into the youngest child's 2nd year -and that has been my experience. My oldest (through lots of different things) has gotten much better as well.
I'm not saying all of this to scare you -just to give you food for thought. You can wait a few years to have another -and since you had such a rough time adjusting to one who was an easy baby -I would REALLY suggest you do that. In a few years, your oldest will be potty trained and he'll be able to communicate effectively with you, dress himself for the most part and play by himself better. When you have two really little ones, there are 2 sets of diapers to deal with and neither one of them can do much of anything for themselves. ALL of the feeding, dressing, changing, bathing, fetching and a great deal of the entertaining and playing is up to you. There are two carseats and two kids to handle in the store. You get the idea.
What is important to you in your life right now other than your son? Do you enjoy having some "me" time or going out with friends regularly? Do you and your husband enjoy going out sans kid? What do you all like to do together -are you big travelers? Do you work outside the home (or from home -but a job of some type requiring childcare)? All of these things are harder and more expensive with two than they are with one. Sitters, daycare -even Moms Morning Out preschools/programs are more expensive. It's harder to get away on your own.
I absolutely love my boys and I'm delighted that I had them, but I don't think people should sugarcoat the experience. We romance having children and having large families far too much in this nation. It's NOT romantic or funny -it's freaking HARD and expensive. There's NOTHING wrong with only having one child either! There are many only children this day and age and many parents who are happy with only one -a lot of them felt like you after having the child they have and don't wish to repeat the experience. I'm an only child who grew up when it was relatively odd, and I still don't regret it! The people who post on here that no one ever regrets having another are misled at best. I know many who regret having another for a variety of reasons.
Do what's best for YOU and your life! If you had depression problems in the past, I hope you got help and if you decide to have another -address it proactively! Take an antidepressant as soon as you deliver if you need it. Good luck and don't let anyone make you feel bad or guilty no matter what you decide!