Although I understand that you do not want to put him under any more pressure, you do both need to have a serious talk about your expectations. You say that he has bought up the subject himself in the past? I am presuming that although you may have had a discussion it did not result in you both agreeing that yes you both want children?
This is too important to cross your fingers and hope that he may be coming round to the idea and you do need to at least agree that your feelings about children are at least both headed in the right direction i.e that you both agree yes you want them but perhaps in another 2 or 3 years.
Also are you sure that you yourself really want children or is it a bit of wishful thinking? You seriously need to be 110% sure that you have changed your mind, especially if your strong relationship could break up on the basis of your desire for kids.
I have been with my partner for over 22 years and right from the beginning we both were very definite that we did not want children, we discussed it and over the years have been sure about each others feelings.
I think that for the moment, you both need to understand that you are both in agreement about your feelings. Have a talk with him. If he tells you he is still unsure, you need to ask him to give you a deadline for his final decision, it would not be fair of him to keep you hanging on and hoping.
Finally this is my opinion only! Children are not the be all and end all! I am sure you know that! Not having children has ensured that we actually have some money to spend on ourselves and enjoy nice holidays abroad without having to save money to afford them. I have watched my sister have a very difficult time bringing up two boys, she has made a good job, but she would be the first person to tell you that it is not all plain sailing (I am sure that there are plenty of others with a different experience though that they can tell you about!)
Hope my thoughts have helped somewhat.
Best wishes
Sue