Like Joe said, it is very good you have chosen to be tested, and very important if you suspect your husband was unfaithful.
You must have some kind of doubt about the trustworthiness of your husband if you have gone so far as to be tested. Correct?
Instead of trying to avoid sex by making excuses, or waiting until the last minute to bring up your concerns if your husband asks for sex , discuss the issue before hand. Set aside a time to talk with him. Explain to him your feelings and the reasons for doubting him. Try not to let the conversation escalate into a fight. Be as calm and assertive as possible while explaining the concern for your health and safety.
This is, in no way, an easy situation. Hopefully your tests will come back negative and you can leave that worry behind you. However, the issue of infidelity should still be addressed so that you don't run across this same situation again.
I hope all is well. Please let us know how you're doing.