@sammy: No, I think this is the opposite direction. You say "don't feel like you have to" not when you feel that the other person is under some pressure, but if you have exerted the pressure yourself. You make a suggestion, the other person hesitates, you notice and try to alleviate the pressure: "Du musst aber nicht", "Nicht, dass du müsstest", "Du kannst natürlich auch anders", depending on context. If you said "Tu dir keinen Zwang an" in such a situation, you would increase the pressure.
Example: You go out with someone you barely know and say something like "What would you think of a cup of coffee in my place?" If you add "Don't feel like you have to", you create (or pretend to create) a loophole for the other person. If you said "Tu dir keinen Zwang an!", you are extremely pushy, implying something like "I know very well what you are up to, so come on, admit to it!"
This is a typical "language lab" discussion, but maybe the request by JadeMoogle US (what a name!) was for a proper translation. In which case, I'm afraid, context is compulsory (to stay with "Zwang" here!).