I understand this.
Part of my intrusive thoughts everyday involve me thinking "This doesn't matter you will die soon" Or make me think that every second I will die and the more seconds I don't die I obsess over the seconds I will.
This goes from mild to moderate to severe depending on any triggers or just how obsessive it gets. Sometimes it goes into health OCD hell and I am really messed up for several months thinking I am dying etc. Doesn't help that I know we all die someday and I don't know what will happen afterwards, its all a mess.
Currently, its just been the nagging thoughts in my head it hasn't gotten to terribly bad, but when it does its awful.
I don't want to age. I am almost 29, but some reason my brain takes that as I am old and going to die soon.
All I can say is use whatever distractions or coping mechs you have. I know how hard it is to compulse out of your head cause it often just comes back. I wish you luck.
I know for me meds and therapy can only do so much, its hard to live with OCD. I really do hope something can help you better.