Magic, Here's the deal you either go or you don't. Your choice and your SO's opinion, thoughts/comments should not enter into your decision. You are separated from him and what you do w/your personal time is your business.
Advise him today of your time off and don't get into a long winded discussion with him. Tell him that you will be taking a few days off at the end of the week, but will do what you can to ensure that the work is completed before you leave on Thursday. Also, advise him that you will not be available for phone calls, texts or emails while you are away.
If he questions you about what you are doing, you can then decide how much you want to tell him about your business. However, it's on him to make assumptions and not for you to add to them, i.e., lie. Honestly is the best way to go because one lie will lead to another and another. You wouldn't like for him to lie to you about his whereabouts...now would you?
This issue is an easy one to resolve...but YOU have to grow some backbone and take your power back. Stop allowing him to control and/or manipulate you. You are not some pet dog sitting there waiting for daddy to come home. You are a grown woman! Now, get to it and tell him of your decision to take some time off.
You are making a mountain out of a mole hill about this little trip. Again, you have two choice go or don't go. Period!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
