I wouldn’t take a class online in a subject you’re struggling in, especially if you are a procrastinator. Online classes can be great if you’re self-motivated and very disciplined, but otherwise it can screw you over by giving you a weak foundation, which is especially bad in a subject that is constantly building on old concepts. I’d recommend trying some online practice (like khan academy) to work on concepts if you feel like you can motivate yourself to put in the time.
If it’s an option for you, I think the best route would be to get a tutor. Not only would you have someone to help you with confusing concepts, but you would have one more person helping you get back on track and make sure you’re preparing properly for tests and learning the material adequately.
Best of luck!!