I had 3 DC's in 3 years. Everyone's situation is different so I'm not sure if my experiences would apply to you. Mine are now 10, 8 and a half and 7. It's relentless, exhausting and expensive, not to mention the strain on your relationship. My bunch weren't really planned but I'm lucky to have a very wonderful DH. I work part time from home.
If you want 3 then go for it but be prepared for a long haul. Try to get as much family support as you can. Things change pretty quickly as they get older and you can esily lose sight when they are very small that you will need big enough accommodation, car, food budget, childcare perhaps and holiday fund to run a larger family happily.
In my experience, dealing with them as babies , yes I found 1- 2 was indeed harder but not as they all get older. Because I had them so close, I actually find it more difficult now coping with homework, organising after school activities, being a constant referee, housework, ( omg the washing!) The endless demands from the primary school every single day drive me positively insane. Our weekends as well are busier than the weekdays now it feels!
I had kids with my eyes wide shut and stupidly didn't think much about how much it would cost to pay for all their needs past baby/toddlerhood. Or how difficult it is to get good childcare for 3 so you can have a meal out with your partner even just once a year. If you have plenty of family support and a good income then fine. It's your decision but perhaps wait another few months if you can. It is lovely to have 3 and I am very blessed indeed despite my moaning here!
It's your decision of course but if you can wait longer it might give you more time to think carefully about what you want and prepare. Society in general doesn't encourage larger families at the moment so it can feel quite isolating as everyone expects you to cope in the same way with 3 children as you do with 1 no matter what your circumstances IYSWIM! I hope it works out well for you and I personally don't regret even for one minute my er... 'crowd' lol! Good luck :)