The good news is that you won't "have a marriage without sex for the rest of [your] life." The bad news is that, based on what you've told us, you probably won't have a marriage for the rest of your life. Sex isn't the only problem. There are three:
1) You haven't done enough laundry together.
Long-distance relationships are tough. But not for the reasons everyone usually thinks--"I miss you schmoooopy!!!"--they're tough, paradoxically, because they're easy.
What do we mean by this? Because you only see the person sporadically, it's easy to miss them, it's easy to cherish the time you have together--Jesus, did we just use the word "cherish?" Slap us--it's easy to sweep issues under the rug. When you only see the person one weekend a month, you never argue about whose friends you hang out with, you never argue over cleaning dishes. You haven't spent enough time doing the simple stuff, the mundane stuff... doing laundry.
SEE ALSO: "She Only Wants To Have Sex Once a Month."
The doing laundry time is critical. Every relationship needs it. Because in the next 60+ years of your marriage there will be lots and LOTS of laundry. Since your fiancé has been on deployments for a good chunk of your relationship, you can always use the distance as a scapegoat. You can say, "Well... I know we have problems...but that's because he's on deployment." Maybe. But maybe the problems are real. And maybe the problems won't go away when he's back for good. The only way to find out is to spend a lot of time together, now, before you lock it in for life.
2) You're young.
Believe me, I hate it when people judge my intellect, maturity, and competence by my age. I always have. I'm sure you do, too. So when I say, "You're young," I know you're rolling your eyes and scoffing at my presumption.
And 21 isn't that young. If everything else is clicking--if you've been dating for years with no meaty problems, if you trust him implicitly, if you see eye-to-eye on all the Big Stuff like kids, money, religion, etc--well... that's one thing.
SEE ALSO: 8 Reasons Your Sex Life Might Have Died
But that's not the case. You started dating when you were a teenager, robbing yourself the chance to date other adults, fool around, make mistakes, and learn more about your needs, wants, and interests. This will haunt you.
3) Sex matters.
Your email describes a man in his forties. It does not describe a 20-something madly in love. But even if he is crazy in love with you, well, chemistry matters. Sex matters. It's possible that he has some deeply-rooted sexual hang-ups (body issues, past failures, performance anxiety, etc.) or it's possible that he's just wired with a sputtering sex drive.
When you choose your life partner, it's not enough to think they're hot. It's not enough that they make you feel good. And it's not enough to be in love. Yes, you must be in love, but you also need to consider stuff like compatibility, values, trust, and chemistry. You can't overlook that last one.
Listen to your instincts. You're worried that things aren't right. They're not.
Don't simply postpone your wedding, put it on indefinite hiatus. Don't plan it. Don't pick out invitations. Don't look at dresses. Don't even think about it. Just...be together, not as future-husband-and-wife, but as boyfriend/girlfriend still learning about each other. If you're absolutely committed to this guy--no ifs, ands, and buts about it--then spend more time with him. Do the laundry. Talk to him about the sex stuff, and if that doesn't work, see a couple's counselor. A pain in the ass? Maybe. But if you're super confident that you're destined for each other, then a year or two won't make a difference in the long term, right?
And if that doesn't work...well, you're young. This guy might not be The One. A lot of others might.
Also, even though it's designed for dudes, take our quiz Is She The One? and see how you do.