You need to clarify what the lab results mean with the provider who did the tests. I'm not sure how to interpret them. Your symptoms do sound consistent with mononucleosis, but you probably didn't get it from the sexual exposure you describe. You can be absolutely confident it isn't HIV.
I'm not a sexuality counselor. Some people will go to the steps you suggest to avoid any risk of STD; others will decide that sexual expression is too important to let such considerations be the predominant ones. For most people, sex precedes true intimacy and permanent commitment. Just using condoms will reduce most of the risk of serious outcomes. And despite all the hype, 99% of sexual encounters occur without anybody giving an infection to anyone else.
(I'm reminded of a movie from 10 years ago, whose name I forget. Albert Brooks played a recently divorced man moving into his childhood home, Debbie Reynolds as his mother. She is dating an elegant older gent. Brooks asks "Mother, you're not intimate with him, are you?" She replies, "Of course not, don't be silly. We just have sex from time to time.")
HHH, MD
From this whole experience, you should learn and now know better than to visit "professionals" as I like to call them. I believe that god, if and whatever god you may believe in, gives every single person one wake up call, being a scare to put one's *** in check. From this I hope you learn a lesson. In the meantime, get checked out for some reassurance. This doctor is highly intelligent and knowledgable in sexually transmitted diseases among other things, just look his name up using a google search. I know he would never steer you in the wrong direction or give you false information. Good luck to you!
You should put this behind you before you are like me or others on here who have lost a few months of their lives to anxiety due to very low risk activities.
And you are correct, stay away from the hoochie mommas. It ain't worth it. "Scared stratight". Maybe this was a blessing that keeps us from going down riskier paths that do put at risk.