Speech development ?

My son just turned 15 months old on the 12th and he doesn’t talk. When he turned one, he was saying little things like mama and dada. Now he doesn’t say anything. His sense of communication is yelling and screeching, you know what I’m talking about😅, I have friends with babies a month younger and a month older than my son and their babies already say things like “hi” “bye” “love you”. I try to work with him on words but clearly no luck. Do you think he’s behind in speech development and I should talk to my pediatrician or is it normal? I know all babies learn at their own pace but he’s been very well developed with everything else they learn and do in their first year of life. I just can’t get him to talk!! Lol