I lost my dad to cancer when I was 8. I am also the first born. I buried the emotions as best I could and now almost 30 years later I'm finally unpacking all kinds of issues in therapy. You are going to grieve eventually. Trust me on this. You can either do it now, or you can carry it around where it will be a constant dull burn, where any time the word "dad" even comes up your eyes will start to burn a bit and the anxiety will rise in your chest. Believe me, and don't become me. It's better to do your grieving now, because the sooner you do, the sooner you can start to enjoy those memories of your dad instead of running from them because you don't want to start crying at seemingly random times. Not to mention if you suppress those memories (which you have to do to suppress the emotions and be "strong"), you will lose them, and from here on out that's all you have left. Don't do what I did. Being this emotionally fragile is not fun, and losing so many memories is a trauma all its own. If nothing else, take time to write them down somewhere safe right now -- you'll want them eventually, I promise.