Should I take the subject tests?

I just took my third ACT. I’m hoping to get a composite score over my second ACT. This was the score from the second ACT:

Composite: 32
Math:31
Science:32
Reading: 31
Writing: 35
Essay: 10

For that test I studied a lot, but for the test I just took I didn’t study at all. However, I felt pretty good about everything but Math, so I may get a better score. For math I’m expecting 27-29. If that’s the case, I’m thinking about taking a Math subject test along with another science to try to lessen the damage from the math section with the Ivy leagues I’m applying to. Is it worth it?

P.S. I did take the SAT twice

Math: 670
Critical Reading: 710
Writing: 770
Essay: 10
Composite: 2150

But I’m not sending it in because the math and the composite are too low. Any suggestions about this?

Well, a lot of people usually take the SAT subject tests in the summer after they are done taking a course (i.e. chemistry, biology, us history, etc). But I know that some colleges take the ACT with writing in lieu of the SAT I and the SAT IIs. However, I don’t think the SAT II Math takes place of your math subsection in the SAT I. They are two separate tests and SAT II math weighs far less than the SAT I.