Does size REALLY matter?

So my boyfriend and I have been together for almost a year now, and we haven’t had sex *yet. We’ve done everything else in between however, orally and what not, and he’s GREAT at it. So I’ve seen what he’s packing, no more than maybe 5 inches. Of course I love him, so duh, it doesn’t matter to me, but I’d hate being so excited then being disappointed in the end. Advice as to what I should expect for my first time?