If that's the size of your .fos file, that's a bit big, but probably okay. If that's the size of your .nvse file, that's ridiculously huge, and almost certainly the cause of your issue. To fix this, you should disable all mods that use NVSE strings, load your game like this, then save it, turn the mods back on and load the new save. Alternatively, you can just delete the .nvse file (but not the .fos). This might cause issues with scripted mods, while the first method will cause issues with mods that add new items (no idea why they would use NVSE strings though). If you have no idea what mods use NVSE strings, you can check the end of your nvse.log file that should be located in your game folder. It might contain information about what mods have strings saved.