I read your opening sentence, and thought, 'wow, how does that even work?'
I mean, how does a loving, open person even be with a serious, quiet, stubborn person oh man, I hate stubbornness as a trait.
But of course, opposites do attract, and these particular traits don't necessarily mean you're incompatible.
There are people out there who wouldn't mind never being told 'I love you' by the person they share their life with. On the whole, they're probably serious, quiet stubborn people.
Loving people, on the other hand, probably can't go happily through life never hearing these words.
To me, this does seem like a waving red flag of incompatibility in your relationship, but only you can know a). if that's actually the case, and b). if it is, whether it's surmountable long-term or not.