Hello Kelsey.

Hopefully this support article is what you need:

https://support.mozilla.com/en-US/kb/Firefox+will+not+start

In any case, you may be having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?

Whenever you have a problem with Firefox, whatever it is, you should make sure it's not coming from one of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode and select Disable all add-ons. If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and theme. You can troubleshoot plugins the same way.

If you want support for one of your add-ons, you'll need to contact its author.

I cannot run Firefox in safe mode, so I can't disable add-ons. I continue to get the crash message when I try to run safe mode. I have been through that support page already, and none of the solutions seemed to match my problem.

Kelsey, try reinstalling Firefox. You can get the latest version (for free, as always) at getfirefox.com.