Saying The L Word

I'm young, but have been with my boyfriend for the best of 4 years...he has never said the L word, not even close. In fact, none of that emotion or feeling ever leaves his lips. Don't get me wrong, he has been totally loyal to me the whole time & is not a bad guy, he's a great one but extremely shy/awkward/to himself about those things.. I said it once a couple of years ago & the favour was not returned. Should i just accept that some people are simply not comfortable with sharing feelings & it will come in his own time? even if it has been 4 years..advice please!