My daughter is 18 months old. She rarely watches TV and we always read books. My problem is, she still can't say a lot of words. I am worried that she might be having speech delays. Has anyone of you had the same experience? Though, my daughter understands and listens to us whenever we talk to her. Am I worrying too much?

Every kids are unique, hence their progression is definitely different. 18months might be too early to gauge if she's having any speech delays. Try talk to your PD, their school teachers, peers' parents to see if this is normal among toddlers of his age. My younger son has the same problem as your girl back then. His progress is quite slow as compared to my elder son; but pd said it's quite normal at that age. Just talk to her and get her to talk more often, everything shall be fine. Now, my younger son is very talkative. ;)