Do you think Gale was gonna tell Katniss he loves her in the First Book? SPOILER for the first book and MOCKINGJAY

He probably did, but then chickened out because he didn't know if she was going to return or not and either way could lead to multiple situations;
She could either
-Not say it back, ruining their friendship for when she returns
-Say it back and make it harder on him if she dies
-Not say it back leading to her regretting it during the Games when she might not return and can't tell him her feelings

Since he didn't say anything he was probably thinking if he tells her that either;
-She would then have too much to worry about it going into the Games
-He didn't want her answer influenced by her future

I think he wanted to tell her he loved her, but was looking out for her by not saying it. Nothing good could have come from him saying it just because there was a chance she might not return, it would complicate her life way more then it already was and had to be.

That's what I've always assumed he wanted to say. Evidence backs it up too, because we know he loved her before the Games. And most likely, he thought it was the last time he would ever speak to her, his last chance to tell her.