There was a short video on the BBC website I saw yesterday with some suggestions on how people with OCD might cope with this. I'll have a look in a minute to see if I can link it for you.
I have been on fluoxetine in the past. I was already suicidal when I was prescribed it and I am still here. It didn't make me worse. In the unlikely event you did have that side effect you would have time to seek support - you won't suddenly and instantly "lose your mind" if that's what's worrying you. You would be in control and able to ask for help.
It's good you managed to start taking it. You won't instantly feel better but if you can just keep getting through one hour at a time for now, it will gradually start to help. I know it's hard to do and really hard to do all the time, but as much as you can try and just bring yourself back into the present moment and the things you're trying to do right now. Not your fears about what's going to happen.
When you do get those periods in between crying, be kind to yourself, take care of yourself, just breathe if that's all you can do. Allow yourself to rest when you can because this much distress really takes its toll on your body as well as your mind and you need to rest. Even if you can't sleep, lying down helps a little.
Some people find it helpful when they find themselves freezing up to make themselves move around, clap their hands, jump up and down, or rub their arms to ground themselves. If you can't unfreeze yourself (or moving makes you more frightened) then just focus on your breathing and being gentle.
I'm not someone who can unfreeze herself - once my brain has decided there is a threat and I need to freeze that's that. So instead I just try to bring my breathing under control, whisper to myself "you're safe", remind myself where I am and try to focus on what's going on around me - how the floor feels under my feet, the sound of birds singing or the washing machine, the colour and texture of my jeans. Gradually reconnecting with the present moment, rather than fears about what's going to happen in the future.
Do you have distractions and soothing activities that help you?
You're putting so much pressure on yourself and that will most likely make you feel worse. You're doing the absolute best you can in very tough circumstances and you deserve to give yourself credit for that.
I don't feel frustrated by you or what you're posting. I know that just because I post something wanting to help, doesn't mean it will be helpful to you or something you can act on or notice a difference from right away. Please don't beat yourself up for not being able to instantly magic away all your distress and struggles - nobody would be able to do that.
I wish I could do something more to help when you sound like you're suffering so much. 