Trouble shooting IR Sensor
Without knowing what parts you are using we can only make guesses.

That said, the fact that your receiver has a "data" output infers it is a remote control receiver. These are usually integrated circuits with an IR sensor designed to receive IR signal modulated at about 40KHz.  The output of such devices will either be high or low (presence or absence of the ~40KHz IR modulated signal).  Such a device wouldn't be suitable for detecting a range of IR radiation magnitude.

Here is a (college) paper on designing a Pulse / Oxygen meter.  If you don't need the Oxygen part you can leave out one of the LEDs and what all goes with it.