Gay/ = vastly different life?

I've known I'm gay since I was like 12. I could be with a guy but I have absolutely no emotional connection with them [in the relationship sense]. But anyway, I can't help but worry about whether I should just be with guys for the rest of my life for the sake of easiness, or whether I should be out and proud. The way I see it, if I act like any other straight person then I know how my life could go - socially accepted relationships, marriage, children, grandchildren, growing old with someone etc. I mean everything is set out for you if your straight. But then it would mean I would have to live a lie. I know people argue that if your gay/ then you can still get married and have children and grow old together, but it isn't the same. Nothing is guaranteed and everything is that bit harder and more complex. I guess I'm just worried that I'm going to get old and end up on my own. It just seems like the whole getting married, having children and growing old together doesn't really go with the gay lifestyle [I don't mean to stereotype here] and from what I've seen once you're not youthful anymore that's pretty much it for you. I know it sounds stupid that I'm worrying about this stuff when I'm only 15 and I'm probably wrong about most of this or just ranting, but what are your opinions on it?