Immediately after an orgasm and only when i'm on my back, i hear and feel my pulse in my left ear, it goes away as fast as it arrived. is that normal?

Not to worry: You likely have some congestion in your eustacian tube (the potential space that connects your pharynx with your middle ear that "pops" when you go up a mountain or in an airplane. ) during orgasm, your BP and heart rate physiologically are increased which is normal and you can hear your pulse in your ear because you have reduced conductive hearing. The tympanic membrane or bones may contribute.