J.H.
Hi A.-
I can speak from experience here :) My first two daughters are 19 months apart. I nursed my first up until a little past a year, so I did a few months of nursing while pregnant and it worked fine for me. My milk supply didn't diminish and I ws no more tired than I was the pregnancy before :)
Having children so close together does have its challneges. I struggled for the first several months and sometimes wished that they had been a little further apart so my oldest could have been more independent when the second came along. However, once they were 2 and 3 1/2 I was VERY pleased they were so close together. They are best friends and do everything together. I am hoping they will continue to be so close when they are older.
I don't feel like having them that close in age short-changes the other in terms of time and attention, not any more than the second child would be in any case. You can never give the second child as much time and attention as you do your first because now you have to divide those things between two children. Now that my oldest is in kindergarten (and when she was in preschool last year), I am getting some one-on-one time with my second child (I also have an infant - her day will come someday!). I really love having my kids close together and wouldn't want it any other way.
You may not be able to get pregnant while you are nursing, especially if you haven't had a period. The hormones released during lactation often prevent pregnancy and if you are not having periods you probably won't get pregnant yet. I got pregnant while nusing, but my periods resumed a few months before. It would be better to start trying to get pregnant after your period returns so you can have a start date for calculating yoiu due date.
Good luck with everything!