Hi, Jou! In the first sentence, the deadline for finishing your work is set to this week. The dates and times you actually need to finish the work by are not specified. In the second sentence, you're saying that you're doing the work you need to finish during the week. The work still must be finished by no later than the end of the week, but there might be specific deadlines within the week for separate tasks. I hope I've helped clarify any confusion. Please let me know if I haven't.

"I got a shitload of work to finish by this week" to me sounds like the work has a deadline that is this week. "I got a shitload of work to finish this week" to me sounds like you have a lot of work to do, but there isn't necessarily a deadline you're meeting, you just have to do the work this week.

LOL perhaps you should avoid using such a vulgar way to measure things but I'll answer. They're both interchangeable cut the former add a bit more urgency than the latter.