First, you confuse sex and love...two different things. A particular form of sex is not the "ultimate" way to show love. Sex is, first and foremost mainly mental. I would say love is at it's best, expressed in many, many other ways.
While I'm not gay, I have had sex and have been in love, so I believe I am still qaulified to comment in this case.
My point is that you seem to equate some special difficulty with being gay as it pertains to sex (and possibly love). Your problem is not unique as you may think it is because you are gay. Heterosexuals experience these same misgivings and problems of approach especially at 18.
My advise is not to obsess over it as everything will happen in time. When there is genuine love the insignificance of a certain sex act being cemtral to the equation will be more than evident to you. You will figure it all out...so relax, and dont let these thoughts color your attitude or approach.