I'm not sure who will read this that needs to hear it but in God, you're more than enough.
Of course, there will be days when you struggle. There will be days when chronic pain makes the journey feel like it's worthless or when your PTSD casts a dark shadow over your life. Weigh those types of days with the ones when your pain doesn't even seem to exist or you're in a great mood. You'll find that the good will outweigh the bad.
There will also be days when you feel like you don't have a purpose, that you were put here for no reason whatsoever. Let me assure you that everyone feels like this. If you'll push yourself to closely examine your life you'll find that there are things you can do from your bed that are worthwhile. It can be as simple as offering someone an encouraging word or praying for them. In God's plan, these things aren't as small as they are in your human mind.
The point is, you were put here (on Earth with the body you have) for a purpose... God's purpose. As long as you listen to Him and let Him lead, you're more than enough.