I feel like breaking my significant other's heart without any notice
Why would you want to break her heart?
She always makes me feel so sick.
You should always be honest with people you love. You should tell them how you feel so you can work on your problems.
I don't care about being honest, I have my reasons to do this.
It sounds like you're very unhappy in this relationship. I recommend communicating that with her and letting her know that she makes you feel really unwell. You may be able to work out your problems by talking about this.