If your last period was on 25 th July, then your due is on 23-25th August, and today is only 15 th. So your pregnancy test will not come positive. However, was your last period on 25 th July, a normal one with usual flow, or was it less/ spotting? If it was less than usual, or had some irregularity/ spotting, you may do a home pregnancy test. Otherwise for your left abdominal pain , I would suggest you to meet a Gynecologist nearby for thorough check up. It may be a cyst or something.