Do you have to send SAT subject tests to colleges?

So I am going to take the SAT US history and Math (not sure 1 or 2 yet) subject test in May. I am not worried about the history one, but I am nervous about the math one. I was planning to take level two since I am in honors pre-calc right now, but I was doing practice questions and I was kind of lost. If I end up receiving a bad score on the math subject test, am I required to send that score to colleges. Also can someone explain to me the college board rules of sending SAT scores? They say you can send your score to four colleges for free until nine days after you take the test? My problem is I do not really know where I want to go yet (leaning of George Washington U right now). Will I be allowed to send my scores later on to colleges? Someone please help I am kind of freaking out!!!

Yes, you can send your scores later on, but you have to pay for them. So take advantage of the free 4 sends now, by choosing 4 colleges you are most interested in at the moment.

but is it required to send an SAT subject test to a college if you do not want to?

With very few exceptions, colleges do not require you to send all subject test scores if you do not want. However, since there are exceptions, you should look at the below link.
http://talk.collegeconfidential.com/sat-act-tests-test-preparation/1912440-must-you-submit-all-sat-act-or-sat-subject-test-scores-p1.html

Since standardized test requirements are at the discretion of the college and are subject to change, you should verify with your targeted colleges.

One option is to only take the US History subject test now, and study over the summer to take a Math subject test in the fall.