Sound advice but ....
I would be more concerned with the apparent disparity between your desire for timing of a family, and your partner's. This is something you MUST sort out before you think about getting married, because otherwise it is going to drive a wedge between you.
I think the fact that your partner is pressurising you - however good his intentions may be - is not a good indication of his willingness to understand your point of view, both practical and emotional.
Yes, having children is fantastic - we have three, but any child must be conceived when YOU are ready, not your partner, you must carry and deliver the child, and undertake the majority of rearing tasks. It seems from your post that you are not ready, and that this is an issue between you.
It may sound harsh, but if you cannot convince your parter of how you feel and why, citing your emotional unreadiness first, and adding the financial aspects afterwards, and he still insists on pressurising you, then i would consider very carefully if he is the right man for you to marry.
Marriage, and children, are about hsaring, and it is clear that you both have seriously different views about the timing of your family.
Talk it over, be straight, be honest, and stick to what you want. If your partner will not see that you have to br eeady for children, then you should have a very serious look at your prospecst for a future, and your wedding plans should be put on ice until you are both clear on the way forward.