Heart beat

Patient: I am in my 30. Weight 98,Height 182cm . I have little bit Hypertension. I will smoke,drink and chew tobacco. Recently i have some problems with my heart. sometime it will stop for second and start with a heavy beat. But some times the beat will be small and fast even i can’t recognize it without through concentration. That time i will be getting fainted for some time. I don’t sure when it will happen. it is happening sometimes i am resting sometime when i do a hard work, sometimes i drink or smoke. i have taken one ECG some time back and the doctor said it is OK. Any body help me to identify the problem