Timer not working as expected

Dear sir,

i want to measure the pulse width of input signal ranges from 100hz to 5000hz.

Below following is my code for initialization and measurement.

i did the programming in polling. not through interrupt.

in this program TIM3-CH3 capturing with wide range of variation in TIM3->CCR3.
please help to get correct value in TIM3->CCR3

configured PB0(TIM3-CH3) in input with pull up/pull down Does it need to be changed

// Timer3 channel 3 initialization.

RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;                     // enable clock for TIM3

TIM3->CCR1  = 0x0000;                        //__TIM3_CCR1;        // all CCRx default 0x0000
TIM3->CCR2  = 0x0000;                        //__TIM3_CCR2;        // all CCRx default 0x0000
TIM3->CCR3  = 0x0000;                        //__TIM3_CCR3;        // all CCRx default 0x0000
TIM3->CCR4  = 0x0000;                        //__TIM3_CCR4;        // all CCRx default 0x0000
TIM3->CCMR1 = 0x0000;                        //__TIM3_CCMR1;       //
TIM3->SMCR  = 0x0000;                   // Slave mode disabled

TIM3->PSC = 0x02CF;                  //719           10usec accuracy
TIM3->ARR = 0xFFF0;                     // set auto-reload

TIM3->CR1 = 0x0000;    // URS =0 -- update request for counter ov/underflow,UGbit,through slave
TIM3->CR2 = 0x0080;    // TI1S =1-- TIMX_CH1,CH2,and CH3 pins are connected to TI1 input(XOR)

TIM3->CCMR2 = 0x0001;  //CC3 config as input,IC3 mapped to TI3
TIM3->CCER  = 0x0100;  //CC3E capture/compare 3 enable

void RpmMonitor(void)
{
  unsigned short int x = 0,y = 0,z = 0;

    TIM3->CR1 &= 0x1110; // disable timer
    TIM3->SR   = 0x0000;
    TIM3->CNT  = 0x0000;
    TIM3->CR1 |= TIMX_CR1_CEN;  // enable timer
        do
        x = TIM3->SR;
        while (x == 0x0000);

        if ( x == 0x0001)             // if only counter overflow skip
        {
                TIM3->CR1 &= 0x1110;  // disable timer
                z = 0x0000;
        }
        else                          //for CC3OF or CC3IF or TIF
        {
                TIM3->EGR |= 0x0001;  //setting UG bit to clear Counter Value
                TIM3->SR = 0x0000;
                do
                       x = TIM3->SR;
                while (x == 0x0000);
                TIM3->CR1 &= 0x1110; // disable timer
                if ( x == 0x0001)    // if only counter overflow skip
                  {
                     z = 0x0000;
                  }
                else
                  {
                     z = TIM3->CCR3;
                  }
        }

}