Hello! I'm so sorry to hear about your Dad. I lost my Dad in April this year, although I'm 26, finished university and working the pain is still so incredibly hard. I think no matter what age you lose a parent it is difficult however for us to lose them on our 20s is more so, not only will you grieve the loss of that person but also the loss of potential memories or experiences. I know for me I have thoughts of him never walking me down the aisle or meeting grandchildren. All I can say is to go easy on yourself, it has only been a few months and grief is a very personal thing. Some people do better to throw themselves back into work or school, others need time with family or friends to heal. I opted for a bit of both, I found work to be a welcomed distraction away from the grief, it was a tiny bit of normality or near normaility for me after weeks of feeling completely lost. I still carve in some time to let myself completely feel the grief- maybe with my mum or my friends to maybe just listen to a song or to look at a photograph. I also found counselling to be a great help, see your GP or university advisor for potential services.  Just remember grief is not linear, you will have awful days or moments but they will pass, and you will have near normal days perhaps even happy moments and you should remember to not feel guilty about those. 
 

Good luck and god bless x