You should say I love you first. And no, you should not be making excuses in your head. Sure, the situation could become awkward if he does not reciprocate your feelings. But those three simple words hold so much weight and meaning to him, and therefore, it is highly unlikely that he will walk away from you without at least giving an explanation.
I know you are scared. Many “I love you’s” turned into goodbyes in the past, and you are traumatized by love because it reminds you of being abandoned. I know you are scared of love and affection due to being left.
But even if it ends up being unrequited love, or even if he is conflicted about his feelings towards you, say it anyway. In love and life, we do not get many second chances, so take these opportunities that come and live without regrets. Be brave enough to make the first step sometimes, and be vulnerable and bold enough to say to the person, “I love you, even if you do not love me back.” Because in a society where we are all taught to be emotionless and dispassionate, loving someone and telling them you love them is quite a heroic feat.
So please, tell him exactly this: Tell him you love him beyond what words can describe. Tell him you love him with a certainty that scares you. Tell him you love him with every single fiber of your being and deep down to your core. Tell him you love him to the point that your own happiness does not matter as long as he is happy and you are willing to go to the ends of the earth to see him smile. Tell him that even if your heart gets shattered into a million pieces, it is a privilege if it means to have been loved by him. Tell him you love him because no one else is as compatible; he fits and completes you. Tell him you love him with a ferocity you can not contain and an aching in your chest that never stops. Tell him you love him the same way he looks at the stars and sunsets, with eyes wide open in bewilderment and awe.
Please, be fearless and reckless with your love. Be passionate and unrestrained with your words. Do not hesitate to tell someone your feelings, even if you get left behind. Life is too short to not at least try, and it is always worth living without regrets.