You could be like me where the idea of love is something extremely selective. I personally can't remember the last time I actually loved someone romantically if at all, but I do feel love in other forms of affection and adoration for humans, animals, cats, newer SS members that work hard, etc. It's a feeling that varies.
Thus it's not that you're incapable, it's that it's something you just don't throw around willy-nilly like so many xian pieces of trash mistakenly do. And perhaps you're just more logical based rather than emotional based - which is just a personality thing.
Though I don't think there's anything physically or mentally wrong with you in this regard, if you're concerned about something spiritual wise, then perhaps it could have something to do with your
Throat Chakra which is the seat of emotions in the human soul. If you haven't opened it yet, then working towards that may help. You can also try meditating on it and see if you can find anything that might be wrong with it.
You may also wish to read this sermon written by HP Maxine Dietrich on the topic of
Love