when i use Wemod for Watch Dogs 2, it take like 18 seconds to start the game, but after 15 seconds, Wemod says its having trouble loading the mods and to try again. When the game finally loads and i click play on Wemond again, it says "to use the mods, you have to launch the game using Wemod, close the game before pressing play ". So im not sure what to do
Hello and welcome to the community. 
- Launch the game first through its launcher (Steam, Epic, etc).
- Wait until you are on the main menu of the game.
- Press Alt+Tab on your keyboard to switch to WeMod.
- Press Play.
- Alt+Tab back to the game.
This is the way that trainers had to be launched in the past before WeMod came along. Sometimes it may still be necessary to use this method if the game takes too long to load the memory addresses that the trainer needs to inject its code into.
Also:
- Make sure you are using the correct trainer for the store that you bought the game from.
- And make sure the game is a legitimately purchased copy, not a cracked version - WeMod does not condone illegal activity, such as the theft of digital content, and hence does not deliberately make trainers to work with them.
I am having the same problem as you and I tried what this guy said and said said to open the game regularly and then press play on wemod but it still says the game has to be opened though wemod there for not letting me use mods