I'm having pain in my left stomach. my next period date is 29 th of may.is it early sign of pregnancy ?

Have u been checked?: "stomach pain" can be caused by lots of things ; may indeed originate outside the GI tract. Further evaluation is in order before anyone can say you're pregnant. Your doctor will want to re-examine you as well as know the quality, timing, duration, exact location, ; associations (eating, position, activity, stooling, urinating) of your pain to better direct the next appropriate testing.

Unlikely : Various types of lower abdominal/pelvic symptoms can be associated with reproductive functions like menses, ovulation, ovarian cyst maturation, etc... Of course, non-gyn causes should always be kept in mind as well.