Don't worry just yet! When I was pregnant with my 2nd baby. I had gone to the doctor at 10 weeks and they found the heartbeat which is the earliest they can hear it. And then when I went back 4 weeks later, they couldn't find it. An ultrasound showed that the baby was behind the placenta and it could only read my heartbeat. And then 4 weeks later after the baby grew more, we could hear it again. But if you're worried then consult with your doctor.
The heartbeat can't normally be detected until quite late in the first trimester, and then it usually takes a foetal doppler to measure it. So maybe your pregnancy hasn't reached that stage yet? The BBC parenting website has very detailed advice on the stages of pregnancy and the tests you are likely to need. But if you are at all worried, you should ask your doctor.
My wife is pregnancy and she is experienceing little bleeding and little pain,she is 15 weeks now , 3 weeks ago they doctor could determine the size etc on the baby ,but after her pain we when by the doctor this morning and do a ultra sound it show the fetus stable and could not detect any heart beat ,the said it is dead .