I'm expecting my second child, i have a daughter. sometimes i feel she is too clingy and want space from her. is this normal pregnancy behavior?

Normal for both: having children is a full time job as you know and you are together so often that it can be she is very attached to you and it can feel to you overbearing at times.

Pretty normal: Starting at 6-9 mo & well into the 4th year kids realize their mother is a more dependable source of comfort/attention/food than any stranger or other family. They also don't have a brain maturity that allows them to realize that when you are not in their view, you still exist. You may feel smothered, but this is normal & improves gradually with age & maturity. Use distraction to keep her occupied