I turn 30 in October and I don't want to celebrate

It is my 30th birthday near the end of October. I don't want to do anything. The most I want to do is buy a tasty cake and eat it all by myself. My dad isn't here anymore, and what is the point?

Of course, I still have my mum and my sister. My sister wants me to come home (I live in a different city) for my birthday, but I'm tired of travelling because I have been up and down this entire year and just spent 3 months on a University exchange in Germany. Most of all, I do not know how to tell my family that I hate coming home because my dad's absence is felt tenfold. I cannot stay in my childhood home because he's not there. My sister makes me share a bed with my mum, meaning that I sleep on his side of the bed every night I am here.

Anyway, despite having the opportunity of a lifetime, and getting to visit one of my dad's favourite cities, I still feel so... lost. I don't have any motivation to do anything and the only thing keeping me going is that I have a job where my students rely on me and my partner who loves me and my family who I cannot abandon.

To make a long stream of consciousness short, am I unreasonable for not wanting to go down to my hometown for my 30th birthday?