Hi Bayuti, it's a tough one isn't it.
First thing stop panicking. whatever decision you make should be done calmly and well thought out.
What you need to do next is think all the ins and outs thoroughly. ie;
who will mainly look after the child ?
how will it affect your/ his working life ?
do you have friends / family, who will / can help out ?
examine your feelings deeply regarding a child of your own. imagine yourself having a child, and what comes to mind ? if it's just fear, well that's natural. if you REALLY don't want a child, then examine why,and what impact it will have on your relationship....
And all the other things I've missed out that you can think of.
Then. and only then, go to your fiance and have a good long chat about it - everything, your fears , doubts, hopes....
Then I think you'll be in a good place to make a sound judgement, and will not regret whichever path you choose, because you can say hand on heart you did everything you could to make the right decision.
Good luck ! whatever you choose those around you, who love you will be there for you.