Hand, foot & mouth disease is peskily contagious - sorry you got it. HIV tests are looking for HIV-specific antibodies (and within the first month post-exposure, antigens), so having another virus will in no way interfere with your test results. If you take a 4th generation test now, you can collect your result.
Of course you will only be testing for your exposure 5 months ago. The encounter 2 months ago was with someone who's negative, and he can't possibly give you what he doesn't have.
What was your risk activity?