Why do some men frequently fall in love.?

My long term partner has spoken of how many women/girls in his past he has been infatuated and in love with. I am curios as to if this is a healthy thing. I am left feeling that, as he is someone who falls in love so quickly with almost anyone, and has thought he has been in love with so many women, any girl that ever want to date him; i am nothing special and it devalues our relationship. I do love this man, and he utterly worships me and professes undying love for me, but knowing he loved so many people before me, really any girl that would love him, makes our relationship have less worth than that of someone who rarely gives their heart to anyone. (For me, i believe it is rare to find true love. ) Any answers as to why certain men have the characteristic of falling in love with women all the time and if i should believe and trust he truly loves me would help although hard to decipher!