Existential OCD

Hey guys. I've posted quite a few times on here and really appreciate hearing some feedback from others who experience OCD, so I'd thought I'd give it another shot for this experience I'm having right now. A couple years ago, I developed a horrible fear of space, planets, existence, and a whole bunch of stuff. It was mainly connected to my fear of heights, and thinking about how we're just floating in an endless void in space made me feel like I'm too high up and I will never be able to touch solid ground in my life. This thought drove me crazy, and I ended up becoming incredibly depressed and unable to get out of bed for a couple of weeks until I changed my medication regiment (have been on 40mg of Prozac since). With time it slowly went away, but it comes back randomly and I'm in a bit of a thought rut again right now. It helps to think about how massive the earth is compared to me, and that thinking about something like space is so irrelevant because I have the whole world to explore. Anyone else have any tips or thoughts that help them bring themselves back to reality? I know it's just a side-effect of my deep thinking, and that I'll be able to get through it. Sometimes it's just harder than other times. Thank you guys!!

If you want to treat this as ocd,then best thing you can do is to trigger habituation via ERP.
works like a charm for me.
First thing to do is to identify source of Fear/anxiety etc.
then you have to train yourself to not run/defend yourself from that fear/anxiety.
point of this is to fight your impulses which could make you feel better.
failing to do so is quite usual so don't get disheartened.
As you are inable to alleviate negative emotion you grow accustomed to source of fear/anxiety, and trough that your reaction to the source weakens and so do your emotions.
read about Exposure and response prevention for professional info.